I came across a post a while back on the New Vegas general discussion about making power armor harder to attain. Someone (Calgone I think) wanted the power armor to break down into damaged and undamaged components when its wearer died. I'm planning to incorporate that into my http://www.fallout3nexus.com/downloads/file.php?id=13361 mod. The way I was thinking it would work, there would be a Power Armor Mechanic perk with at least two levels. Level one would let you recognize and loot the components, to sell or stockpile. Level two would let you reassemble them into working sets of power armor at work benches.
I haven't written the code yet that determines which components remain undamaged when a power armor wearing NPC is killed, but it will be dependent upon limb condition, and I'll try to set it up so that the only way to salvage intact power armor would be to kill its wearer almost exclusively through head shots. I've also got something in place already that detonates the nuclear microfusion pack if a PA wearer is killed with a torso shot, and that will probably render the armor almost completely destroyed. It might be two or three weeks before I have all of this done, but I think it will accomplish more or less what you're asking.