I think that ought to be our goal even if it's realistically unachievable due to the need to keep the game balanced. The whole point of enfeebling ought to be disabling the foe to the point where it's significantly less of a threat, and I don't feel Red Mage really accomplishes that.
I agree. Though I do think we can all agree that TP moves are the root cause of this problem when we take away the issue of 'Spell Immunities'.

This, and 'Auras' which seem to be a nice trend in Abyssea (Does Voidwatch have these?)

So a Debuff that would lock down Sphere effects and prevent them from taking effect would be a good idea for a new debuff, if this idea of Auras are going to be a new mechanic.

But getting back into the idea of attacking TP moves. There's only a set number of ways of doing it.

Stun prevents it (enemy keeps TP).

We have TP reducer moves (Straight TP , or DOT)

TP Gain suppression (Between Subdle blow and other BLU enfeebles.)

Max TP down is a new debuff we've seen.

Then we have "Delay increase." Alla Addle.

Alternatively, perhaps a more advanced, alternate version of stun that 'prevents' a TP attack on a timer, and causes a TP reset, would be an incredible boon for fighting TP moves.

Other Debuff categories we haven't touched?

Magic Defense reduction.

A debuff that enhances Skillchain/Burst damage.

A debuff that causes the monster to deal damage to itself rather than the party. (Could be incorporated into that "TP Killer Stun.")

I think those are enough to chew on for a while.