Well I've been looking at this since it began. This is just an idea not very good, but it may work.
1.Make up an animation of the path, set it to frame 1 on start.
2. when you drap the matching part on to path it plays the next frame and you distroy the part.
things to do, pin collision box to the parts and have new one appear at the end of each animation of the path
so the part would have to collide with that new collision box each time.
Well that's my effort not very good sorry, I'm a total newbie