Removing MP would be kinda....off? for me. Something about it seems strange.Taking TP, MP and combining them with stamina would make battle more userfriendly and create a unique feel for each weapon and job within.
I would keep MP, but remove TP and do something like what they did with Xenogears battle system.
Have three types of attack, weak, moderate, and strong. They would each use stamina, and the player could string them together to create weapon skills. You would need enough Stamina for each attack. Maybe even keep auto-attack and have auto attack be equal to strength as the "weak" attack, but instead of needing Stamina it generates stamina, along with a natural stamina gain like there is now.
This way I wouldn't have to use more than 3 of my ability slots to have access to my WS's, I would just need to know what combo to use to create the weapon skill. This would also require WS's to be tied to the actual type of weapon, which I'm totally for.
I'm just throwing ideas out there, maybe something will stick or spark ideas in others.