If Embiid is 100%, Simmons doesn't matter.
We forget how good Embiid was before he was injured, and he's worked on his game, how many 7'2 centers can hit the three?
He's freakin' HUGE these days.
I think you listed the problem though, trusting that he is 100%.
Also when he gets into his first game (which here I am assuming next season), he would have not played competitive basketball in 2 1/2 years. Don't get me wrong, I am truely hoping he comes in and beasts it, but I do think it's smart when planning the future to not automatically think of Embiid.