1. One option Christopher Foley mentioned was something like:

NOTE: If you change the variant secret in the Push Admin UI, you need to rebind your app to make sure the `mobile-services.json` file is correct.

2. Am i correct in saying that multiple variants are never represented in mobile-services.json? ie rebinding won't work?
If so, I think your idea to document that as a 'known issue' is the correct approach for this.