Do you mean 1 switch can do tap & on/off? Not sure how that would work, since the pedal wouldn't know if your turning it on/off or changing the tempo. Maybe there's an opportunity for some innovation here (2 quick taps means on/off, but of course this means you couldn't tap in a short delay). I'd probably prefer just 2 separate switches.
If you mean 1 switch for on/off and a separate switch for tap, then the tap switch would not need to interface with the relay bypass board at all.