I just emailed BillM (billmaudio.com/) with my idea about a Dark/Bright footswitch and he responded almost immediately:
"The only downside of routing the bright/dark tone switch out of the amp is that it's a low-level signal between preamp stages. Any excess wire would dull the tone and it would also be very susceptible to hum."
It is great that we have people like Bill, Tavo and others that are so willing to share their technical knowledge with us!
"Everything louder than everything else!"