Will the game allow this somehow? Or is junk and weapons and non-power armor the only things that can be scraqed?

You could try dropping it, and then entering construction mode and seeing if that will let you, I haven't tried though. Could work, you can scrap pretty much everything you pick up, save for consumables etc.

Just tried that. It doesn't work: the Scrap command is greyed out. Looks like the only way to get repaid of extra Power Armor pieces is to sell them.

Hm, well that kinda svcks I guess. I've got tonnes of bandit armour to shift.