Back on topic!
I've been pondering mechanics for a Spellblade/Mystic Knight/Rune Fencer/whatever for some time now, and while I have a couple basic ideas as a start, it's still very simple. I'm largely tackling this from the perspective of someone whose experience is mostly with caster jobs, but who has recently been leveling DRK and DRG, so my apologies if it sounds too familiar to start with but there's plenty of room for expansion.
So first and foremost, I do feel somewhat inspired by Duelle's concept for a Red Mage rework, which largely takes the melee combo we already have and increases its uptime. 1-2-3 melee hits, third hit gives a proc that will make reduce the cast time of your next spell a la Dualcast, and your next spell can be a choice between a damage buff (such as Imperil) or a hard-hitting magic attack (TBD). Before we get to branching this is a pretty standard structure for most melee, and not too dissimilar from DRG's Wheeling Thrust/Fang & Claw mechanic.
Secondly, and as I've said several times, there's a plethora of sources we can use for inspiration for a Spellblade in terms of filling out kit abilities:- Commando, Ravager, Synergist and Saboteur abilities from FF13, including Flame/Frost/Spark/Aqua/Galestrike, Blitz/Area Sweep, etc
- Warp Strike and Armiger skills from FF15, as well as the Link Strike ability we copied in the crossover event
- Rune Fencer's Harbor Runes from FF11
- Celes Chere's Rune Knight abilities from FF5
- Rune Knight/Sword Saint (and similar jobs) abilities from FFT
- En-spells from across the series
- Virtually every job with a "Spellblade" command throughout the series
- Probably any with a "Swordplay" ability, since aside from Samurai there is a surprising lack of sword-wielding jobs who actually use those skills
- Some skills from Kingdom Hearts, perhaps?
However, the minor downside to this is that several of these skills are distinct in terms of elemental typing, which is largely irrelevant to 14 without an elemental wheel. Thus, skills like Flamestrike and Sparkstrike would have to either be merged or made fundamentally distinct from one another. As RDM took the former route, I'm not opposed to the latter.
So for a small sampler platter I prepared:
Resource gauge tracks the current Enchantment timer and stocked Runic Charges.
For the time being, consider all attacks in each "Chain" section to be interchangeable within each step of a combo.
Chain 1 attacks:
- Smite: Deal unaspected damage to the target
- Sparkstrike/Thunder Stroke: Deal minor lightning damage to the target and gain Enthunder, causing auto-attacks and weaponskills to chain additional lightning damage to nearby enemies; mutually exclusive with Enfire and Enblizzard
- Nightblade: Deal minor damage to the target and siphon off a percentage of the damage dealt as HP
Chain 2 attacks:
- Flamestrike/Flametongue: Deal fire damage; if used as a combo action, gain Enfire, causing auto-attacks and weaponskills to deal a modicum of additional fire damage and inflict a stacking DoT effect; mutually exclusive with Enblizzard and Enthunder
- Froststrike/Icebrand: Deal ice damage; if used as a combo action, gain Enblizzard, causing auto-attacks and weaponskills to deal a larger amount of additional ice damage and return MP; mutually exclusive with Enfire and Enthunder
- Aquastrike/Liquid Steel: Deal increased water damage to the target; does not interfere with current enchantments
- Blitz: Deal damage to surrounding enemies, inheriting the element of your active enchantment
Chain 3 attacks:
- Galestrike: Deal wind damage to the target; if used as a combo action, gain Quickening, causing your next spell to become instant and reducing its GCD
- Whirlwind: Deal damage to surrounding enemies, inheriting the element of your active enchantment; if used as a combo action, gain Quickening, causing your next spell to become instant and reducing its GCD
Spells (5 sec cast time apiece):
- Imperil: Deal minor unaspected damage and increase target vulnerability to your magic damage for a modest MP cost
- Banish: Deal heavy unaspected damage to a single target for a high MP cost
- Alterna: Deal moderate damage to the target and diminishing damage to nearby enemies for a heavy MP cost
For each use of a finishing spell, the user gains a Runic Charge. Upon accumulating 3 Runic Charges, the user has access to one of two Finishing moves:
- Ars Arcanum: After a cast time, unleash a devastating multi-hit melee attack on the target
- Aetherial Slice: After a cast time, unleash a wave-motion attack against enemies in a cone before you
Gap closer:
- Warp Strike: Throw an aetherial blade toward the enemy and teleport to it, dealing damage to the target; 30 sec CD
--> Improved Warp Strike: Allows the accumulation of charges on Warp Strike, allowing it to be used twice in succession
--> Link Strikes: Allows Warp Strike to be used on allied targets as well, restoring the target's HP and causing your next Warp Strike within 15 sec to critically hit
Ranged attack:
- Strike Raid: Instantly toss your weapon at the target in a spinning slash before summoning it back to your hand. 20% chance to gain Quickening in the process.
Other oGCDs:
- Breaker Blade: Deal Earth elemental damage damage and extend your current enchantment's duration
- Tempered Saber: Increase personal attack power and accuracy for a short duration
- Endrain: Enchant your allies' weapons, causing all weaponskills and spells to siphon off a percentage of damage dealt as HP
- Runic Shell: Create a barrier, absorbing magic damage received by all allies for a brief duration to charge your own MP
Rough idea is:
- Chain Smite -> Flametongue -> Galestrike -> Imperil to open or keep debuffs up
- Chain Smite -> Liquid Steel -> Galestrike -> Banish as your core combo to build up to Ars Arcanum
- Weave Icebrand in place of Flametongue/Liquid Steel when Flametongue's DoT stacks to its maximum
- Chain Thunder Stroke -> Blitz -> Whirlwind -> Alterna for AoE damage to build Aetherial Slice
--> Alternately, Thunder Stroke -> Liquid Steel -> Galestrike -> Alterna in two-targets
- Spam Strike Raid at range unless a proc comes up to cast a spell
- Nightblade to recover, since Bloodbath won't really be an option with all this magic damage now will it
Again, plenty of room for expansion and I would love to hear others' ideas or critiques. All names are placeholder (though I do like the idea of a Water attack inheriting the benefits of other skills).
I can see a Spellblade wearing the same Maiming/Slaying gear as a Dragoon, for a more Knightly feel to its armor than MNK/SAM/NIN. My question at this point is what kind of weapon it would wield -- likely some kind of sword, but there's still some wiggle room there. You could go with Hand-and-half swords to represent its fluidity between styles sort of like Alisaie before she switched to RDM, or call back to its more Middle Eastern outfit in FF5 and say curved swords -- sabers, scimitars, falchions, dao, khopesh, shamshir, etc -- like BLU did in FF11.