We replaced a starter about a year ago on a 330Xi A from underneath. Just to prove it could be done.
What a huge PITA. I think my forearms are still scratched. Didn't save much time but reduced the chance of follow on issues, as much less was taken apart in the process.
W/O my entire toolbox and years of know-how it wouldn't have been possible. It still required 2 technicians here and there.