Yes, I see. Personally, I prefer the clear dichotomy of it either being stock or somehow changed. It really is a matter of choice how you like and view your own guitar. I just changed the pickguard and knobs on my Squier 50's Classic vibe Tele. I think of it as a Partscaster that I created...
I like the first part of your definition but the second half seems contradictory. I would like to suggest that basically if your guitar is not in the stock assemblage from which it left the factory, it's a Partscaster, mods included. If it is modified it is no longer a stock model. I would...