Frobius, I think you're being a bit alarmist here. You're assuming that putting different types of tyre on each axle will suddenly make the car unstable in some way. That would be basically saying that the tyres would have completely different levels of grip and performance. I would suggest that as long as they are capable tyres, what difference could it make. Traction is the main concern here, the car and road don't care whether its a run flat or not, as long as traction characteristics are similar.
I wouldn't think putting standard Bridgestone rft rears on, and having the exact same tyre but non rft would turn the car into a death trap. Aside from one being rft, the grip characteristics and tread pattern should be pretty similar.