Imagine Regen like this -
you charge the move successfully, and then it is active for a given period.
When you take damage, the player reacts normally however stamina is transferred to health.
It's an interesting way to make Piccolo adapt to competing with many saiyan classes with more transformations. As a superfluous embellishment, imagine the player is killed [by a ki attack] while the move is activated, the player is switched for the 'armless' version. When they come to a rest, they stand up, regenerate their lost limb, and continue playing with sudden death health.
Just random ideas, I simply find this amusing because I've always thought this particular Regeneration was so challenging to successfully incorporate into a game design.