to do bar spins with brakes all you need is a detangler, like a Oryg. And yes, mech discs will work fine with one. it may not be as smooth...but if your in the road, then you need to be equipped for the road....it's like fixies who go out there without a front brake...it's their risk.

plus a front brake is not all that hard to deal with in any weather...even on my tmn bike going fullo-bore, I can put the brakes on hard enough to lift my rear wheel, and still be able to keep it in check. Emergency stops are easy when you have your modulation down...now unclipping could be the problem

I've had some fun ones where I had to swerve since I couldnt unclip in time. It comes with the territory.