I went with the second option.
I don't mind giving up Nesmith and I really don't care at all for Romeo. Fine with giving up a pick or two. Would rather not give up Smart, but willing to if it came to that.
He's not a big name, but he's putting up 16 PPG on 50/40/80 this year along with strong defence, and his combination of length and athleticism allows him good versatility. The loss of Hayward is a big reason why the Celtics are playing so much worse this year, and Barnes would mostly fill in that gap.
Having a starting 5 of Kemba/Brown/Barnes/Tatum/Theis would also give Boston a pretty big overall lineup that could switch very effectively on defence, and every one of those guys can score from three, from midrange and inside. It would be a touch matchup.
We would miss those big game winning defensive plays that Smart makes from time to time, for sure. But we'd also miss some of the big unforced turnovers and bad shots he has a tendency to lose us games with as well. I think swapping Smart for Barnes would make the team less volatile and more consistent from game to game, which is something this team IMHO desperately needs.