Note, the Octagon and other projects already have a rotary program select knob. A simple diode array is used rather than an 8 to 3 encoder IC.
I found out that the FV-1 has 8 built-in algorithms in addition to the 8 in the eprom... so for a 1 of 16 selector, you could use an up-down button to drive a 4 bit counter or similar (e.g., like https://www.ti.com/lit/ds/symlink/sn74f163a.pdf).
Yes, you can order your custom set of programs right here: https://www.pedalpcb.com/product/eeprombuilder/ . Just like ordering your own pizza, I'll take glimmer, chorus, flanger, with extra delay please.
Hexe's website is definitely worth the visit, he has an FV-1 controller computer board, as well as an awesome 4 W tube amp. Tons of stuff there.