This is great stuff Michael!

"PastePart" looks fantastic, actually, more functionality than expected :) it's more like "AssemblePart"
How is "PastePart" activated, new icon or command via keyboard shortcut, is it going to act like Import where you choose an existing part as you mentioned and where will the origin be for the part that your bringing in, position as modeled?

Sorry for the barrage of questions but this looks so good, well thought out, well done Michael.

Cheers
~Danny~