Why do you want it?
IMHO mid level tint, especially if you can't park inside, makes sense. Beyond that it just seems like you're trying to hide something. Plus, significantly-darker-than-legal tint shouts "hey officer, find a reason to pull me over!" Why go looking for trouble?
My 335i is untinted - just whatever's built into the glass itself. I've had 35% all-but-windshield before and it was fine, then in another vehicle it was just the rear seat and back windows. Both came that way. With my 335i I've not felt the need to do anything different from stock, though I might if I didn't have a garage at home and a parking deck at work. That said, limo tint would look stupid on an E93.