My initial thought regarding Bill's "let them have kits" response above was "heck no" but; I have to admit that after pondering this for a bit; I have concluded it would actually be fun to occasionally assemble cars or engines from kits. Like many on here; I grew up in the era when we assembled model ships, planes and cars. I can remember some of the aircraft and particularly the ships had a tremendous number of small detail parts that had to be removed from sprues and added to the model. And in retrospect; it was all quality time!
Since my layout has more or less been completed for a number of years; I have started to find enjoyment in some minor weathering and detailing of rolling stock so; assembling rolling stock and locomotive kits seems like a logical next step in that progression.
Curt