The last post shows that it is possible! And he even stripped the back!
Honestly I don't think you will ever want to remove and reinstall a cage. You could go the route of an add-in roll bar. I know they make one for the E90 and E92 (E93 no idea) so you can run racing seats and a harness without a cage. They also are somewhat removable if you only do a few events per year.
Track / Autocross setup: Forgestar F14, w/ Toyo Proxy R888 & RA-1
F: 18x10 et25 285/30/18 (21.8lbs), R: 18x11 et32 305/35/18 (23lbs)
355mm StopTech | 96 Octane
Laguna Seca previous record - 1:49:498