Are you aware that you can load in insturments to various parts, then save the lot as a patch set? This is a snapshot of the synth at that time (and includes things like volume panning and keymaps) Reloading this either by name, or by using the 'recent' list is a very fast way to restore everything and will do so regardless of what changes have later been made to any of these. Well… I didn't know that actually, but I need solution that can change voices during playing song, that's why I'm using Mididings...
If you check again, you'll find that changing bank within a part, does in fact change it for the entire synth. Well… to be honest, I'm checking that all the time, and I see no problems with having different banks on differents parts at all. Maybe we misunderstood each other (more possible, I don't understand you, or I explained problem wrongly :D), but that's how I change sounds: Click on sound name of Part 1 in mixer, Select Bank for Part 1. (for eg: 115) Select Program for Part 1. (for eg: 44)...
Well, firstly I thought about using just built-in banks and sounds from Yoshimi without mangling with it. I found voices I wanted for songs, but unfortunaletly they are in different banks. I would argue (as a simple user) about non-individual channel banks, cause it's possible in GUI to choose different bank for different channel (or in Yoshimi naming: Part) and not only for whole setup, so I consider this should be possible to do. Well… it even (almost) works, so that's why I reported this as a...
PS I'm using yoshimi-1.5.1.1-1.fc25.x86_64 from Fedora repo.
Changing Banks via MIDI signals causes to change banks on wrong channels