Hear me out a sec because I know a lot of people have an instant negative reaction to any kind of change. I think it's worth taking a moment to consider the implications of removing MP from the game. Please wait to read it all first before making a reaction.
MP is a bit of a relic which I think has run its course and now has fewer pros than cons. You're already regulated in how often you can use your powerful job actions by recast timers. The most noticeable lingering effect of MP is being a restriction on how long healers can sustain dpsing before they run dry, especially in spamming aoe dps moves like Art of War for minutes. You want to keep doing aoe dps in big pulls when healing isn't required but MP gets in the way eventually.
It also creates some oddities when MP management is used for a job mechanic instead of a job gauge, with BLM being the only job to guzzle consumables (super ether) to extend its rotation (triple flare or despair). The solution there would just be making a mana gauge for blm and drk to replace the outgoing MP resource, with the triple flare rotation being preserved by making manafont into a charged action (2 stacks).
We're already half way to removing MP by culling most MP utility actions (Manashift, Refresh) with only Lucid Dreaming remaining. Now I think it should just be removed entirely so healers can dps without restriction and without needing to keep pressing Lucid on cooldown. It's kind of an uninteresting band aid button like the old Invigorate for TP.
PROS
1) Healers can freely dps for long periods if MP is gone.
2) Remove some more UI clutter and further reduce memory footprint of HUD elements. Many jobs (War, Drg, etc) don't use MP already but still have the resource displayed.
3) Unify job gauges as the only resource management tracker for all jobs, also eliminating ether consumption for certain jobs.
4) Cooldowns/recast timers and casting times are already sufficient to regulate the use of spells, with MP being a superfluous resource layered on top of that system which rarely affects decision making. If resurrection was free, it'd still have a penalty in the form of a very long cast time if swiftcast is on cooldown. Rdm doesn't have to deal with cast times but its verraise could just be changed into an ability with a 30s (or so) recast time if the MP cost penalty is no longer a factor.
CONS
1) Have to repurpose ether type items and possibly some enemy actions like Magic Hammer.
2) Some people may have a nostalgia for MP in Final Fantasy games I guess, as is the case with Protect.