Hey,
I have seen some people in Japan running solely rear brakes. I always thought that was stupid, but I have been thinking about on and off for some time. Now I recall they were using those aerodynamic spokes (with no hole) which cannot fit the front brake. ... I suppose having one of any form is better than having none (for safty point of view).
T
P.S. You guys shouldn't go single brake on SS. If you do, you have only one single system of braking; and if that fails you have no backup. I seem some people doing it, and it scares me.