Extreme Regeneration and Costs HP

[Kfireblade]

Would you guys allow a character who has extreme regeneration to take costs HP as modifiers on advantages? Got a player who wants to but I'm not to sure I'm ok with that. I mean, Its a high point value game so they should be very powerful but this seems like a broken combination to me, especially when he also has ATR. take an advantage for -80% because each use cost 8 hp, use it your first turn, then heal all the damage up your second turn....