A few others that I don't think have been brought up.
Ekpe Udoh had a great season last year in a backup role with the Jazz. Maybe he could provide some depth.
Khem Birch might run out of minutes quick with Vucevic, Bamba, Aminu, Gordon, and Isaac ahead of him. He was highly effective last year.
DJ Wilson has fallen out of the rotation in Milwaukee. This has the added bonus of Wilson having an axe to grind against the Bucks if he is traded away. He is a legit 6'10'' with a 7'3'' wingspan. His defensive stats in limited time have been pretty good.
Bjelica is a very intelligent player that works hard, but has definitely defensive deficiencies. Still, he would immediately be the best shooter on the Cs, which helps open the lane for our drivers.
What about our old friend Kelly Olynyk? His numbers and minutes are down a bit. With Bam playing well and Leonard (surprisingly) finally be effective, as well as the Heat playing Jones, Winslow, and Butler playing the 4, and Johnson coming back soon, Olynyk might be falling out of favor. He'd probably be the best all-around big the Cs had (I'm a big Olynyk fan).
For that matter, James Johnson might be a great option. The last two seasons, he's been one of the best defenders on Giannis. The Heat will definitely know this and probably keep him for a potential matchup in the playoffs.
WCS could be another option. If the Warriors blow it up this year and try to get as much draft capital as possible, the Cs could trade for him. He's an athletic guy who has figured out his role pretty well. Still, I'm not convinced he has the basketball IQ to be the answer against guys like Embiid.
Just a few thoughts to add to the list.