1a for your global cooldown complaint, NO NO NO, NEVER EVER. i enjoy ff 14 combat BECAUSE i dont have to spam 80 button presses a bloody minute, if you want this so badly, go back to wow/ rift, shoo, off with you.

piety adding mana regen... it does in a sense, as mana regen is based on max mana, though piety doesnt affect it much (6.5 mp per point iirc)

also changing the gcd would require the game to rebalance EVERYTHING.. also you can lower the gcd by stacking spell / skill speed

1b theres plenty of variation between classes, the "homogenisation" you claim with tp and mp and changing that directly contradicts your request for more cross class things. as you wouldnt be able to use any skills from other classes because you dont have the rescource.
also most classes play vastly different...