[Suicide Junkie]

That's irrelevant.
You can add regen ability to things other than armor components if you want them to be regenerated.

To go with your example, if you were to say, skin your zergling alive, then the hide in your backpack isn't going to contribute anything to the zerg's regeneration capability any more.
The best way to model the starcraft physics is to give all the regen ability to the hull, and give the armors themselves the regen ability so they can be regenerated, but with an amount of zero. (or an insignificantly small amount if nessesary)