I think if you want to go for a light ride, just go and get a whole new bike. Use your old ride for a back up and a beater (rain, bad roads, nasty conditions).
Agree.
When you look at most light bikes, it's not just the frame but the net of
all the parts that give you the light weight. I think you'd go mad trying to shave weight part by part, and in the end just waste a lot of money.
Wheels are probably the exception, but here there are potential benefits other than just weight.
-spence