+1 to me for mount-observe - rpi-imager already has udisks2 which provides similar functionality to enumerate mounts etc. removable-media is perhaps a bit more tricky, since as per the Process for aliases, auto-connections and tracks we only would typically grant this for media (sound, photo, videos etc) management applications - however given that rpi-imager flashes images to external devices, auto-connection of removable-media does not seem unexpected to me. The final part then is related to the publisher - whilst this is not published by the official upstream, @popey would definitely fit into the category:
if the snap is published by someone other than upstream, the publisher must be vetted and either be an established committer to the upstream or the wider snap ecosystem (eg, an established well-known contributor to the software itself, a member of the snapcrafters group, etc)
So +1 from me for auto-connect of removable-media for rpi-imager as well.