Off the top of my head I can't think of an offer that would make me do it.
I'm a strong believer that the only way Simmons can excel on a team is if he plays the Center position, where his lack of outside shooting becomes less of a liability and where you can still put his rebounding, athelticism, playmaking, and defensive versatility to good use.
Problem is that if you were to do this you'd need to trade Rob Williams, as you could never have Rob and Ben on the court at the same time, and he's become too good/valuable to bring off the bench.
so at this point you're now talking about giving up Jaylen Brown AND Rob Williams in order to bring in Simmons - and I think that is a pretty clear step in the wrong direction.
A package built around something like Marcus Smart + Rob Williams + Romeo Langford for Simmons is something that I would consider if the salaries could be made to match up, but I'm not sure the Sixers would be interested. Even if they are, it's a deal I find interesting but not necessarily one I would be overly excited about.
And It would be contingent on Simmons' willingness to give up on the idea that he's a PG.