There's also the issue of taking in Griffin's salary. He'll make $20.1mm next year, which means that the Celtics will need to send out at least $15.1mm in salary in any deal. That could be done by trading Bradley ($8.3mm), Crowder ($6.3mm) and Young ($1.8mm), for instance, but then adding a BRK pick on top seems like a very high price for 1 year of Griffin. Maybe LAC would take their 2019 draft pick back instead.
BOS gets Griffin
SAC gets Crowder and Young
LAC gets Bradley, Gay and 2019 LAC 1st rounder
BOS lineup - Horford, Griffin, Jerebko, Smart, Thomas
BOS bench - Johnson, Olynyk, Brown, Hunter, Rozier +1
BOS bench/D-league - Mickey, Bentil, Jackson, Nader
Europe - Yabusele, Zizic
BOS would need to sign up a wing shooter for the room exception.
It saps the team of its depth and causes a severe lack of wing shooting, so I don't see this trade working out.