I like the idea, but not the implementation. Maybe make it more like the second wind use. I definitely don't want them putting a hard cap on healing most of the time (can't use a healing potion or get most healing spells once you run out, for example).
Then again, I'd prefer them separate HP from THP (temporary hit points). Make HP physical wounds (and a much smaller pool), and make THP everything else players like (stamina, luck, skill, divine protection, morale, and the like). Also, make all THP be consumed before HP is taken away in most situations (things like falling might bypass THP). THP returns extremely quickly, but HP takes a while to get back. Let things like the 4e Warlord class heal THP, while the cleric heals HP. Both have their niche in combat, that way. That is, THP will need to be healed more often (go Warlord!) since it's consumed first, but wounds are long lasting and you need a Cleric (or the like) to stop someone from bleeding out (go Cleric!).
Just my preference, but I know people don't like the divide. I really, really doubt we'll see HP split like that, but it's worked very well in my RPG. For my group, that is. And we're definitely not representative of anything other than ourselves... As always, play what you like
