So, small personal fantasy: I'd love to see a javelin-based tank added to the game. This would be:
Shield and throwing spear-based. The range on the throwing spear wouldn't matter a lot of the time, but it would give the tank an interesting kit for fights that involved short phases that were away from the boss, allowing the player to continue their rotation even when away from the enemy.
"Lightest" defensive kit of the tanks. Obviously, we'd be talking about a percent or two, but still - very slightly the least brawny tank.
Highest mobility tank.
Fair amount of self-sustain.
The javelin is an underutilized weapon within Final Fantasy, but has a really long and impressive IRL basis (javelin warriors frequently carried javelin-sized quivers on the inside of their shields, allowing them to throw multiple projectiles in a battle. They could be as effective on-foot as they were riding as passengers in chariots, affording the driver both protection from arrows, and ranged offense against foes). It's also not well-represented in MMORPGs... I want to say only LOTRO prominently features a throwing spear + shield class.
I understand that this has a low-percent chance of happening. But would you play it?