So, basically this is a Smart for Rondo type deal? (How you proposed we would use the 8th pick). I would say no.
Why?
Well, this is how I thought of it.
Rajon Rondo
Pros: Champion, 2 time All-Defensive 1st team (2 time 2nd team), 4 time all-star and most importantly a proven commodity.
Cons: Working back from his injury, 27 (almost 28) is kind of old?
Marcus Smart
Pros: To keep it simple -- potential.
Cons: A hot-head and has "bust" potential.
I just really don't see Marcus Smart being a future star in the league, which, quite frankly, is something Rondo already is. I just don't see the advantage to doing this trade you are proposing. Things are also looking up right now with the whole Kevin Love ordeal.