Then let me re-phrase my statement. Torsos. You can have 3 - 6 mech builds to tinker around with.
Godmode, Lavascope and Hellfire armor are good torsos that people generally use. Diamond shell is tough.
Man... I wish I could have a fully upgraded torso.
But yeah, I see your point with regards to having a thing to hold upgrade power... hmmm... perhaps building our own fusion kits? That way, we can declutter our inventory, while saving them off for future upgrade.
This would be helpful for old players with a crapton of inventory already, and with fully fused weapons, too.