Re: Extreme Regeneration and Costs HP
 

Fast regaining of (HP,ER,FP) are among the things that break things a lot. So before allowing any such I have to think what limits I want to put on them. The exact limits and methods of course depend on the campaign. But a "Allow everything" simply does not work for such.

The classical ER 20-100, extreme regeneration ER(150) and then buying all powers at high cost FP (10-20 depending on how often you want to use them) and you save a lot of points at high end games.

The same works even better with cost HP if you have high HP as cost HP is not multiplied by your HP/10 but the healing from regeneration is.

In the low end games the issues come up less, but the OP asked about extreme regeneration and in that case there should be an actual disadvantage to a limitation.

Re: Extreme Regeneration and Costs HP
 

That's certainly a PoV with a right to exist and with some reasonable support by arguments.
My point is that your concerns look at a grander issue that the specific of Extreme Regeneration. They're about the fairness of pool regeneration in the broader sense.

Re: Extreme Regeneration and Costs HP
 

I would probably price fatigue regeneration at 10/level, each level gives +1 fatigue per minute (so 6,000 points for extreme). If you want a tireless character, build your abilities to not cost fatigue in the first place.

Re: Extreme Regeneration and Costs HP
 

Fatigue recovery is fairly easy anyway. A character with Breath Control can recovery 1 FP every two minutes of rest (with Fit or Very Fit, 1 FP per minute of rest from FP not spent on magic or powers). A character with HT 16, Fit, and Breath Control-16 just needs 32 minutes to recharge their batteries (16 minutes if recharging FP not spent on magic or powers). The same character requires one day to heal one point of HP, meaning that the difference of recovery is a factor of 1:7,200 (or 1:14,000). And FP regeneration already starts at 1 FP/minute for 50 points because you avoid having to spend time resting.

Re: Extreme Regeneration and Costs HP
 

Yes, my concerns are broader than just what the Op asked, but the reply I gave was about the specific issue. It is based on you should not get free points as stated explicitly in powerups 8. So to not give those free points the things has to be forbidden, extremely heavily reduced or made so that it is still limiting.

Some other have proposed either disallowing it totally or reducing it a lot, my solution is to allow it if the player wants it and they get the full benefit but at a cost of having it limit them. Which of the solutions to pick is up to the GM.