It would be kind of weird if the whole bidding war was actually Philly just trying to get in front of the Lakers to take Jackson. Problem for the Celtics of course is Fultz doesn't make it past the Lakers so whatever Philly's motivation is kind of irrelevant to what it means to the Celtics (other than, of course, the idea for all the Jackson lovers here that he won't be around if you trade down to 3, which might make this move seem worse to everyone).
In a world where the Sixers aren't willing to do #3 and return the Lakers pick to move up 1, could the Celtics step in and provide the difference?
Something like:
Celtics get: Swap rights to the best of the 2018 BKN/PHI/LAL picks (basically tank and ping pong insurance), some of the Sixers 2nd round picks.
Lakers get: #3 and second of those three picks, Okafor
Sixers get: #2 and Avery Bradley, and a promise the Celtics aren't taking Jackson.
Motive for the Celtics - shed Bradley's salary to clear room for Hayward. Allows them to keep Rozier if they want (though they have a lot of guards). Nearly guaranteed a top 3 pick next year.
Motive for Lakers - they get a pick back next year, gamble on Okafor
Motive for Sixers - they get their man this year, they get Bradley, they shed Okafor.
These of course are just meandering thoughts based on a single tweet. So take them for what they are worth.