@ Betelgeuzah. With every ability (spells included) they are all subjected to timers, Reason I would split the TP/MP/Stamina bars would

1. Increase the battle pace.
2. When paired with the stances, removes the limiting factor.
3. When removing the Stamina bar to allow auto-attack, Limiting factor is that some abilities (Normal attacks) have a second nature (Light attack = Defense boost, as well evasion. Pummel = increased TP gain)
4. This system would allow the stamina bar to stay in place (main global timer for attacks) without limiting the effects of certain attacks.
5. Spells and enhancing abilities also run off a timer. so there is no need to place them on the stamina bar.

My knowledge is limited to GLA and PUG ( as those are my mains GLA R50, PUG R33 )

As with the auto-attack. with it on would only remove spamming of the main attack buttons (personally I like pressing them). The player will be able to focus on positioning, stances as well finding more ways to use the system to increase their damage. Allowing the freedom to send messages without completely hampering game play.

This idea will tailor to both those in favor of Auto-attack, as well against it (would like full control of their character)
both sides are subjected to the same limitations with neither gaining the upper hand.

Not 100% sure what you refer to on Tags so I am sorry. still very new to Forums.
will try to figure out how to place my in game data at the bottom of my posts like I see on others.
Hopefully this cleared up any questions. Thank you for reading.