Do the Celtics really need LMA given what they already have on the roster and at the cost it would take to get him?
Celtics aren't at the position yet where they need to make a move and cash in on assets yet. They could but they certainly don't have to.
I think this trade would significantly improve Boston's chances against the Cavs/Warriors
Smart, Olynyk, Zeller, Jerekbo, 2018 BKN
for
Aldridge, Mills
I think that trade makes reasonable sense for both teams.
So post-trade
PG - Thomas, Mills, Rozier, Jackson
SG - Bradley, Green, Hunter
SF - Crowder, Brown
PF - Aldridge, Mickey
C - Horford, Johnson
Team is a bit light in the interior depth (though is right now anyway), but I think that top 8 (Thomas, Bradley, Green, Crowder, Brown, LMA, Horford, Johnson) would pose a lot more problems for the top teams than the current team does. And there would be 2 roster spots available to add some veterans for the stretch run. Now is that team a future champion, maybe not, but Boston is legitimately only 1 move away with that team and still has top tier assets available to acquire said player (17 pick, Brown).