Water Cannon - Building pressure buff mechanic (no timer on buff), every spell cast that's not water cannon adds 50 potency up to 200 (total potential being 320 potency, pressure consumed on water cannon cast).
Weaving it in feeling less like going from god mode spell 1k damage to a lalafell safe squirt gun. Also with a change recommended later in the post this will help maybe actually want to use it lol (whorl and needles).
Sticky Tongue - It's cool, good positional. Shorter cast time might feel nice but its good.
Bomb Toss - This isn't an important change but one that I think would be fun. Bomb toss is now nearly instant (0.5 second ish) cast, dropping a bomb at location that will go off in 2 seconds (as you see in many bomb mechanics). This allows the visual feedback fun that is a bomb, and also gets you back into the action faster (an issue I see with nearly everything being 2.5 second cast lol). Short cooldown added to bomb toss to compensate for the new lack of cast time.
Faze - Fazed targets become fazed, gaining an evasion down (that also effects the chance of chance based spells blue mage has) for 15 seconds (stun mechanic not removed). Faze is highly accurate skill.
Blood Drain - Maybe later restore mp will be helpful but right now it's a big "..lol why?" (so far at least). Adding something else would be really nice, perhaps a blood infusion buff (invigorated). Greatly increased mp drain effectiveness at half mp otherwise adds invigorated buff: spells cast 15% faster for the next 30 seconds (still drains mp but not super effectively).
Ice Spikes - Casting water spells increase the duration of ice spikes by 10 seconds (up to 30). Slow debuff is now called chilled. When a chilled target is chilled twice they'll gain frostbite (attack and cast speed are now slowed (20%, boss exceptions probably apply here), movement further reduced (40%)).
Acorn Bomb- 30 second aoe sleep is pretty strong lol. When equipped blue mage has increased sleep resistance (causing sleeps to not last as long and go to full resist sooner).
Self-destruct - Hopefully they plan on adding a reraise spell to blue mage, in that scenario it might be more interesting to add a longer cooldown to this skill and increase the potency further (and perhaps share that cooldown with final sting). Otherwise it's a fun goof spell, does what it needs to be (goofy).
Final Sting - Same thoughts as above, if there is a reraise blue mage spell then these could see an increase in damage and share cooldown. Otherwise it is what it is.
Mind Blast - Add rattled mind debuff - interrupted spells while under the debuff cause the enemy to take an additional 50 potency every interrupt (helpful against heavy casting enemies).
Bristle - Next 5 potency based spells damage is increased by 30% (no timer, reset to 5 spells if recast - doesn't stack past 5). I feel this will make it more fun to use while being management light. Instant cast, has cooldown (so you will probably plan it for a rotation of strong spells). While under the effects of mighty guard the damage reduction from mighty guard is ignored (nullifies mighty guard damage down, will not add 30% in that scenario).
1000 Needles - 1 second cast, has 25 or so sec cooldown. To make it less painful to use but also less abused, also part of the reason other spells are being buffed (I feel the optimal 1k needle spam is a bit of a downer on other items in the kit but if you take away this spell then things slow down /a lot/ - a check should be ran after the change to see if other skills need any further potency up buffs or not).
Toad Oil - Increases evasion by 15% when equipped as a spell, permanent slick buff. When cast increase the effectiveness of the next poison and fire spell, has cooldown. (Self-destruct potency increase, flamethrower gains range and cone width, bomb toss aoe and potency increase, bad breath effects last longer, eruption has a secondary 25% potency eruption that follows up - the interaction will be listed on the named spells not a big paragraph on this one).
Level 5 Petrify - The drill combo is nice (420 potency), I'd say all physical blue mage spells should have this (plain-cracker for example, 100 tonze swipe and swing if those become things as another example). Faze increases chance to near 100% (of equal level monsters that are a multiple of 5), cooldown added. If spell fails cooldown is not triggered.
Plaincracker - Unless Blue Mage gets to learn Titan's stomp it could be fun to give this that sort of repeat cast mechanic. Increasing the MP cost each consecutive cast but also reducing cast time, such that it becomes reminiscent of Titan's repeated stomping (but is not a maintainable activity).
Alternatively for each enemy petrified by you gives this ability one charge, up to 10. Stack does not reset except for on death/job change/logout. Ability is now instant cast, will recharge over 15 seconds if there are no stacks (will not passively gain more than 1- the rest must come from petrification or other blue mage mechanics).
Flying Sardine - Looking forward to seeing a shark skill added to this game, like those sharks that charge an enemy. Slapping an enemy with a fish adds chummed waters, adding an interaction with the shark rush skill :)
Bad Breath - Toad oil will make these effects last longer.
Dragon's Voice - They already have a fun combo, hit them with ram's voice and get 310 potency spell on dragon next.
Ram's Voice - ^
Peculiar Light - 30% magic down is nice. When waxing buff (moon flute) is on peculiar light can be cast to set waxing buff to 30 seconds (from any value, like 1 second remaining). Can be cast during waning debuff, in which case all enemies nearby will also gain your debuff of waning with whatever time it has left (which is basically a super form of pacification debuff).
The Look - A combo with one of the haka like spells the birds have in the sea of clouds could be fun.
Drill Cannons - Combos with petrification
Glower - Mighty guard damage reduction ignored and width of the beam increased when cast after the look
4-Tonze Weight - 40 heavy for 30 seconds is pretty strong given you can cast it at range even. Combo potential with any spell that has to do with gravity or lifts them into the air to crash back down :)
Aqua Breath - Looks a bit sad with 10 potency. Reminiscent of the guildhest with the malboro perhaps aqua breath if cast after toad oil creates oily bubbles that will explode after a short time offering a stacking poison debuff to those in range (something like the guldhest mechanic). If desired remove the dropsy mechanic when using toad oil, such that you will blast them with the non-physical bubbles and shock them (high voltage) and then combo with toad oil for physical bubbles that explode into stacking poison debuff with further combo opportunity via feather rain.
Diamondback - 90% damage reduction, lawl.
Eruption - Toad oil interaction
Feather Rain - Any toxic (oily) bubbles from aqua breath will become poisonous razor plumes, adding damage to their popping damage on top of the dot rain applies.
Fire Angon - Add cooldown and allow it to last on the ground for a short duration, any fire spell cast while on the ground will cause fire angon to pulse it's effect (100 potency). This includes the secondary eruption from toad oil and each tick of flame thrower.
Flame Thrower - Channeled skill that triples MP cost each "tick", like the machinist PVP flamethrower it'll apply a dot. Toad oil will cause the mp cost to double instead of triple.
Flying Frenzy - Jump attack, cool.
Glass Dance - Chilled/frostbit take an additional 100 potency and frozen enemies shatter dealing an extra 50 potency to all enemies nearby the shattered foe. (Chill comes from blizzard spikes, frozen from ram's voice).
High voltage - Works with dropsy (aqua breath) to increase potency (130) and duration of paralysis to 30 seconds which isn't bad. Would like to see the damage buffed, either direct or upgrading the dropsy dot into a different one.
Ink Jet - If it's blind like Paladin's blind then eh, if it's blind like a single player FF game then.. oh boy it's good lol. Can't recall but if there is any spell in the game that is sort of writing like then this could combo cutely with that (like if there is some library gubal book/writing related ability).
Loom - Can be used during diamond back (if that's possible). Using loom removes up two debuffs (that are esuna able). Costs 15% mp, doubling every consecutive cast (cost resets after 7 seconds). Instant cast. Combo with another ghostly spell to double range might be a neat hat trick.
Missile - Faze will help land this more likely. Imo with faze combo the % chance for non-boss monsters should be near 100% but add a cooldown. Failed casts will not trigger the cooldown.
Mountain Buster - Petrification combo, deals more damage than shock strike to a single target (but less aoe damage).
Sharpened Knife - Damage is not reduced by tank stance. Increased potency that is based on enmity held and position in the party ranking up to 500 (extra) potency. Add a decent cooldown.
Shock Strike - Extra potency if cast after water cannon, aqua breath, or fish slappy. Has better aoe sharing damage spread than Mountain Buster (but less single target).
Snort - 20 yalm cone knockback is situational but could be helpful. Can be cast without cast time if used after bad breath.
Song of Torment - Sleeping enemies will have night terrors, they will not wake while taking 75% increased potency ticks but the duration lasts 50% as long (at the end of the terror they will wake, ceasing the sleep as well).
Tail Screw - Faze will increase chance to near 100% on non-boss equal level enemies, has significant cooldown now. Failed casts will not trigger the cooldown.
Veil of the Whorl - While active: Water cannon's max pressure increased to 300 potency (420 total potency potential, before potential offensive buffs), gain 100 potency per pressure building (instead of the normal 50). Aqua Breath has increased range (creating more bubbles if cast oily).
Off-Guard - Actually pretty convenient use (even resets itself if you kill them)
White Wind - Imo blue mage should get another self healing spell (shark rush + chummed water?) but this is potentially a very strong team skill lol (very).
Mighty Guard - The damage decrease is pretty intense, but I've suggested a few ways to get around it already above (also to note for people who don't know 1k ignores this)
Transfusion - With reraise it could be neat, otherwise.. eh? Transfusion being a combat raise could be really helpful (can cast on the dead and living for a full raise and or heal), especially if it's blue mage's only raise (outside of reraise). Reraise having a cooldown being a balancing element (somewhat lol, it'll still be strong).
Moon Flute - Add a short cooldown and allow loom to remove waning nocturne :)
Doom - Faze will increase chance to land to near 100% (normal enemies at least, perhaps less so on secondary boss), has lengthy cooldown. Cooldown doesn't activate unless successful (with an exception listed later). Cooldown is notably reduced for each enemy killed (that you have participating levels of hate on like other mechanics in this game, doesn't have to die by you but you have to be active in it's death). If it fails on a boss (doom is said to never work on the final boss of an area) cooldown is set to 60 seconds and deals 500+ potency.
Edit: Not a feedback but just wanted to add a skill I thought could be really helpful in the skill list for blue mage-
Molt - Allows blue mage to create a molting of themselves taking some damage, staying in position of casting location, and taking any markers on the blue mage when cast. Meaning you could move a tank buster marker, or stack marker, off yourself and onto your molt. Name and visuals are unimportant, just that concept of being able to drop mechanics off and the shield part making it more helpful so you get greater use than just very specific fights. May leave a decent cooldown and charges on it or other concepts to encourage skilled play around these fights, so you can't just mot every single issue thrown at you (which would make it a bit boring).