I think you have to do a DPE and Boston 2018 1st for Evans if you think you can make it to the Finals this year. Evans scoring punch, ability to rebound from the wing position and his very good passing skills coming off the bench for Boston makes them a serious threat to win it coming out of the East.
Also, if Evans loves the team, city and culture perhaps he takes a 3 year/$30+ million contract from Boston to stay. Heck if we are going to give that type of contract to either Evans or Smart next off season, I will take Evans every time.
You can always use the MLE to resign Baynes or upgrade from him.
Lastly, who cares about a late 20's 1st round pick this year. We have almost too much youth on the team as is and could be in possession of 3 more 1st rounders in 2019. Let the players who are young grow and then decide if they are worth keeping over players we could draft in 2019.