I've actually thought about an enspell that absorbs TP.
It certainly would address the issue of a Rdm TP feeding and also boost their damage in the process.
It wouldn't even necessarily need to absorb more then the Red Mage deals. I mean other jobs feed some level of TP. This spell could just help lower Red Mage to more their level since Red Mage really does feed a ridiculous amount of TP.
There's a few issues with that though.
1) It would severely limit any kind of TP altering enfeeble in the future as this stacked with that would practically destroy the possibility of monsters TPing with the right set-up
2) It would be very difficult to balance. The spell would either give a very small amount of TP back or would virtually let Rdm melee solo stupidly difficult things from never feeding them TP. The spell can't ever pass 25% of your base TP since any more then that and 50% SB and +50 agility pretty much means you don't feed TP. The only way for it to pass 25% would be for it to factor in AFTER SB and Agi and well...if you are subbing /nin this spell will get destroyed since the TP will already be reduced quite a bit after SB and Agi. It would be VERY difficult for this spell to surpass the damage our current enspells can do while still keeping it balanced unless it did some form of damage itself.