Thanks for getting this started, given that the current syntax for release is based out of positional commands such that this is what we have:
snapcraft release <snap-name> <revision> <channels>
There is either a possibility of a new command instead of release (e.g.; promote) or use the same release command to also allow something like:
snapcraft release <snap-name> --from <risk> --to <risk> [--arch <arch>]
This does ring some warning bells in me for which a new command might be much more clear, something like
snapcraft promote <snap-name> <from-channel> <to-channel> [--arch <arch>]
<from-channel> and <to-channel> would accept the track` part of a channel.