I don't know much about it & apologies if I misunderstand, but if you simply plumb the rear m/c up to one front + rear disc, & leave single front disc on normal front m/c, won't your m/c:piston ratios will be all wrong?
KB
So ? Don't let that trivial stuff get in the way of an idea ! I guess you could hook up the integral brake to the front brake lever and the foot brake lever to the single front brake caliper.