I've had to remove rivets on my C60 when I moved the mounts around during the Cadi V8 swap. I found the easiest way is to notch the head of each rivet crossways like a Philips screw using a die grinder. Then each of those 1/4 segments just flies right off with an air chisel. Wear safety goggles and earplugs!! Especially the earplugs, because wow does that air chisel get loud when you're subsequently knocking out the plug portion of the rivets.
I was sure grateful for pneumatic tools that day!
