Why? Just curious, as to their exact purpose. They could just be variants, but wouldn't they just be the same thing?

i'd guess because the heavy only has 2 low slots, even at prototype level. so it suffers from a serious regeneration issue.

though 2 counterpoints to that:

1) that's probably intentional. the heavy is still underpowered at the moment but i would rather see the heavy weapons restored than their armor even further buffed. people focusing on the armor are missing the point. ccp never gimped that part (except on the militia suit)

2) does the heavy even have a big enough PG/CPU advantage for this sort of thing to matter? i mean assuming they ever actually carried a heavy weapon, which draws more than the light weapons. if they're not carrying a heavy weapon, then that really just supports my first point. the problem is the weapons.

maybe, but that sorta requires heavy weapons being fixed anyway.

but yah i get it. it opens up different styles of build, use an intentionally low tier weapon in favor of better sustainability.