No need to apologize. That is a good site to know about.
The 2 heads into 1 cab switch does exist. I think Radial make a switch called the Headbone which does it.
It's more complex than an A/B because it needs a dummy load and I think, a make before break switch.
Toe-Knee, I can't see if those enclosures are pre drilled
maybe I should just invest in a drill bit, don't want to fork out for a bigger drill though.