Not offering to do it, but just brainstorming a little.
I think the switching could be accomplished using analog 2x1 mux functions. That is, your pushbutton for "A/B" would actually first go into a T-type flip flop (like the crossed transistor/cap circuits you see everywhere). Then you'd have a logic signal that would alternate between 0 and 1 for each button press - that's your "select" signal.
Then you double up on the pots and assuming the top and bottom of each one is GND and +V, and the wiper just goes to a chip somewhere, disconnect the wiper from somewhere, connect the old wiper to a 2x1 mux input, connect the new pot's wiper to the other 2x1 input, and the switch toggle signal to the mux's select line. Then the mux output goes back to "somewhere". Do the same for the other two pots. If that's NOT how the pots are wired then it becomes more complicated.
Assuming that the mode selector switch is simply a 1P6T rotary connecting pulled-up signals to ground 1 at a time, then the last mux gets wired as a demux. The input (the 1-side) would get connected to ground and the output would get connected to appropriate mode pin. If you wish to be able to select any mode for your two settings, then you'd have to get another 1P6T rotary and then you'd have to connect the demux outputs to the common pin on each rotary. The "selected" rotary switch would be able to ground the mode select line through the demux and the other one would just be waving in the breeze awaiting its special moment.
That's a lot of assumptions though!
Keeping in mind my strong bias against soldering, and the thought that all these little wires would be somewhat fragile, if the intention was to gig with this I'd go so far as to suggest getting two RV-5s and just use an A/B switch to select the one you wanted. OK, OK, I realize half the fun is conceiving and building it, so don't let me ruin your fun.
