I just made and installed that switch today and I don't think it's really that complicated, though I am still just and Electrical Engineering student, so correct me if I step out of line.
First of all, 7.5 amps isn't that much, so just go with something small like 14 or 16-gauge wire.
As for the switch, what difference does it really make whether the switch has to be on or off for it to work (really there's no practical way around the "on-to-work" method, because when a switch is off, the circuit is broken, thus no power is being supplied to the TC or ABS). And if it's really that big of a problem, just mark out the "On" and "Off" labels on the switch and you won't know the difference.
Also, most standard switches that you'll find laying around or in the general interior electronics section of you local auto parts store are rated between 10 and 30 amps. A switch simply touches and pulls apart 2 pieces of metal to connect a circuit, so you're not going to hurt it by under powering it.
And, finally, if anything does go terribly wrong and your switch/fuse can't handle it and burn out, then your ABS and Brake lights will come on and you may have to replace the $0.10 fuse.