BOS trades: Brown, Hauser, Pritchard, Scheierman, Tilman
BOS receives: Giannis
A third team might be needed to take on some of the outgoing salary. We have no bench, but we're a below second apron team.
KP
Giannis
Tatum
Brown
Jrue

As long as we are over the 2nd apron, we can't do a trade where we send out multiple players to match the salary of an incoming player. Giannis makes more than Brown so I don't' think this trade works unless all that outgoing salary (Hauser, Pritchard, and so on, about $23M)) gets us under the 2nd apron. Is that the premise? I didn't work the numbers relative to this specific trade but every time I tried to work something out, I couldn't. BOS salary is a rough estimate at best. We would have to replace all those outgoing players with something, rookies, min salary vets, whatever.
MIL wouldn't be able to take back more than they send out either as I think they will still be over the 2nd apron (if they have Lillard + Brown plus the rest of a roster), so the "extra" salary would have to go to another team.
I would trade Brown for Giannis. I love Brown, but Giannis is better. He would pair great with Tatum.