Short update: Things are dragging along a bit as we moved house and our second son was born a couple of weeks ago.
A tech-savvy user built the current development tree of the sd2snes firmware and made a short demo video. It shows how a YAML file containing cheats is supplied and the cheats are in effect:
v0.1.7 preview 4 will be available in a couple of days. It will also feature a text-based configuration file so in-game hooks (and a couple of other things) can be configured via text file while I am working on the GUI.