I don't think you trade Embiid over Simmons. Embiid is a clear top 10 player in this league right now. Sure his health issues are a real concern, but they would be for the acquiring team as well (thus diminishing his value). Now if some team came with a crazy offer, you listen, but if they trade one, I think Simmons is that guy. That said because it is fun, here are some interesting trades for Embiid that make some level of sense for both teams (some work this season, some work this summer).
Embiid, Horford for Towns, Dieng, Culver
Embiid, Horford for Collins, Reddish, Parsons, Crabbe, 2020 Protected 1st (lotto), 2022 Protected 1st (lotto)
Embiid for Gallinari, SGA, 3 of the wealth of 1st's
Embiid for Favors, Ingram, Hayes, NAW, 2020 protected 1st (top 5), 2022 1st