I figured Blue Mage could use a few more job abilities and there didn't seem to be a thread for just those ideas. Here goes.
Equilibrium: If activated with less than 100 TP, converts the necessary MP into TP. If activated with greater than or equal to 100 TP, converts all TP into MP.
Cooldown 2 minutes.
I've always been annoyed with the problem that arises with chain affinity. You can either wait for it to finish it's cooldown, or weaponskill and hope you get enough tp by the time the cooldown is ready to use it again immediately. This job ability would solve that problem, allowing you to reach 100 tp instantly at the cost of 1-100 mp depending on how much tp you already had when it was activated. On the flip side if you're in need of mp, or you're not in a position where you want to weaponskill, you can convert that tp back into your mp pool instead. You could use this as a tool in all sorts of ways, like getting a quick weaponskill off like flat blade, or kickstart your aftermath effect. If you're fighting a monster too tough for physical damage, you still get the benefit of your melee strikes in returning an extra 100-300 mp back.