IF you know what are you doing AND have a good machine / STEADY hand you can drill the head of the screws with a small drill. I did that with a few screws on an e71. After the head is off the rest of the screw is easy to remove.

Make your way trough the head as slow as possible. Stop often and check how much metal there is left, you don't want to drill the surroundings. When you're almost trough the head will snap off, you can do it without touching anything else but the screw head.