Nope- Exum doesn't excite me too much. In limited time in the regular season (and this summer), Smart looks like Exum's older, more talented and polished brother. Actually they don't look a like at all, Smart is just better.
I also don't think that Utah is so willing to get rid of a top 5 pick from last year- this would signal a failure in their management/scouting very early. They are most likely going to hold on to him, unless someone gives them a dumb offer. While I am not advocating for the Celtics to use all of their draft picks, Exum is not the guy I want to build around by trading future assets.
Demarcus Cousins, Marc Gasol, Al Jefferson, and Chris Bosh are all guys I would try to trade draft picks (plus players) for down the road, once this team is good enough to compete with just that one extra piece.