Um is this not why they gave DNC Finishing Moves? The only time you have to worry about tp is at the beginning of a fight, until you build up finishing moves. You can generate 5 Finishing move points in 20 sec with Presto. You have to put Merit points into the category that grants you more tp / finishing move and cap it, which will give you 750 tp for all 5 finishing moves at cap.

Not saying you don't have a valid point, I'm just saying that there are ways to get extra tp within the actual job, but Auto-Regain would probably make DNC a bit too overpowered.