Every weaponskill, spell and ability should use MP. Change my mind.

[Xelanar]

As it currently stands MP might as well not even be there. No job requires MP management, unless resurrections are required. Removing MP from casters would change nothing, because they never run out anyways - or in case of BLM run out at a set pace.
Simply adding MP cost to every skill and ability of every job will not make jobs more fun to play, if that cost is not relevant in some form.

Also running out of MP would not be fun. If it does happen for whatever reason, the player would be forced to just sit there and wait. Which means there would have to be some way to regain MP for every single job.

Jobs are already way too similar to each other, and recent changes to BLM show the team is not even done with homogenization yet. Having a universal requirement for MP regeneration in some form would just homogenize them even more.

[Misutoraru]

From ARR until SB (Storm Blood) we had TP as a resource that melee would use. Sprint also consumed TP.

Thank god they get rid of TP. Still remember running ARR dungeons just waiting for my TP to regen while my caster teammate could easily spam AOE like no tomorrow.

[Xelanar]

Thank god they get rid of TP. Still remember running ARR dungeons just waiting for my TP to regen while my caster teammate could easily spam AOE like no tomorrow.

As an AST, buffing a TP regeneration Spire card into oblivion and putting it on a Melee DPS during dungeons felt really good. But other than that, having TP on Melees was a horrible experience. AoE was so expensive too.

[Azurarok]

I've assumed TP/MP management's gone for the same reason enmity management's gone and healers only get glare spam.

My understanding is that it was the role of a Phys Ranged to assist in refilling those bars, and that meant one's overall rotation and output was affected by your party composition and competence. They've been furiously designing away interdependence between players outside the DDR body checks and mit checks.

[Valence]

You know what is affected by party competence too? Healing. Oh wait, they made tanks invincible for the same reason...
( are we still playing a multiplayer rpg game ? )