Hi - with BLU getting an upgrade soon, why not enjoy and theorycraft how BLU would potentially fit into the current PvP system:
Now for starters, we'd probably have to decide how the typical BLU job flavour would translate into the game. In previous installments, the core gimmick is learning enemy skills but there would be few options here:
A) They'd have to get hit to use the spell - meaning it would either be passively available all the time OR having to activate a counter like button first to learn the next spell they get hit with (which would probably be too hard to implement in such a fast paced environment) Support spells would also not be available in such a scenario unless you have pre-defined spells based on the job that attacked you as (say you'd get a healing spell if you'd get hit by a White Mage etc.) allowing them to have up to 19 learned spells atm.
B) Use the lancet type of learning akin to GNB for a more controlled usage (think Kihmari FFX). This would make it somewhat similar to GNB without altering the rest of the kit.
Depending on that, their gimmick will probably be 1-2 buttons already, leaving about 10 skills more in a 12 active button layout:
1 - Goblin Punch as the basic filler spell that has (slight) damage variance as its gimmick like in previous games (we're talking about up to 2k bonus damage here nothing special)
2a - Mighty Guard as the defensive spell, it usually includes protect/shell/regen so a damage down, a small shield and either a regen or CC shield like Aquaveil
2b - White Wind as their defensive spell, equally as iconic would heal based on current HP around the Blue Mage that might make them too much of a primary focus though..
3 - Bad Breath as their CC spell, very iconic to their kit could host a whole slew of status effects from poison, heavy, blind, paralysis, mini - it would probably have to be like bio blaster plus 1 random non-stunning effect in a cone
4 - Level 5 Flare as their damage spell, see since the level x attacks are quite ingrained within the identity but damage with a huge radius around the caster would make it work
5 - Learn as their unique Job identity as discussed above - could temporarily get access to a foe's attack based on which job it was. Alternatively assign a Primal spell to each of the 19 jobs that would be replaced instead (like getting hit by a WHM would give you Lakshmi's Strotam etc.)
6a - 10000 Needles as their utility, this would function similar to MCH's drill as it would be a flat damage in a straight line regardless of guard - since drill can do double damage but has to rotate through other spells, I think it shouldn't do more damage as tradeoff but granting a sprint for mobility instead would be possible
6b - Magic Hammer as their utility, as I think depleting someone's MP would be quite powerful depending on how much it would be (like 50%?). Still it would feel unique enough especially with their LB being Mantra Magic
6c - 10000 Needles as their utility, this would function similar to MCH's drill as it would be a flat damage regardless of guard - since drill can do double damage but has to rotate through other spells, I think it shouldn't do more damage as tradeoff
7a - Frog Song as their LB that would transform people into toads for 2s akin to Miracle of Nature - of course this is a highly controversial skill but as LB it'd be justified as it would be the similar to the dancer LB
7b - Mantra Magic as their LB, flat out swapping HP with MP would cause mass panic in an area, especially paired with a previously used Magic Hammer
7c - Night as their LB, puts everyone (friend and foe) to sleep which would require precise targeting to be useful but it feels underwhelming as LB
8 to 12 - Recoup, Purify, Elixir, Guard and Sprint
(as much as I like Self-Destruct, it would have to be paired with a re-raise from Angel Whisper to not be a complete joke - maybe being able to revive immediately without a timer but even then the damage would have to be high depending on the HP used for that attack)
Hopefully the devs will consider implementing BLU into PvP as their skillsets are wholly replaced in the wolves den already