The great thing about signing a max contract this summer is that it will look cheap compared to most of the contracts signed in 2016. That alone is reason enough to pursue any of the "more than the MLE" to max guys available.
Besides the more obvious choices at small forward (Butler, Leonard, Draymond Green, Harris etc.), I would love if we pursued Khris Middleton. He is elite from behind the arc, and an underrated defender. I think he would be even better under Brad Stevens.
I would also make an offer to Paul Millsap as a power forward. I don't get how he can keep such a low profile, he is a star on both ends of the floor. And his play in Atlanta should easily adapt to Boston. I would take him over Love (and I like Love a lot).
There are a handful of interesting centers out there, too...