I think that if the Ui could use a user defined device/midi channel then you could define midi message to do pre define tasks for example:
on your web config you show all midi devices attached to the Zynthian. like Zynthian Midi in, Roland 800pro on USB etc.... You select what device will send the UI midi data and on what midi channel. then a list of parameters and corresponding midi command. For example.
devices attached to receive UI midi commands "USB Midi 1"
Midi channel: 16
go to the next snapshot: Program change value 1
go to the previous snapshot: Program change value 128
Master Volume: Control Change value 7
I see the the need for use in live performances not necessarily in the studio.
So at the studio I have created all my Snapshots such as horns using a sampler the next is strings and so on. I just need to on my midi guitar or foot controller send a program change 1 and go from horns to strings and then send program change 128 to go from strings back to horns. no need to touch the Zynthian,
on the Idea of snapshots would be nice to be able to make groups of snapshots. say set 1 and set 2 and inside your group is your snapshots. so from the snapshot menu you could choose a group and then see all the snapshots and pick the one you want.