REQUEST: Please consider publishing firefox nightly as a separately installable snap.
The Firefox snap is published directly by Mozilla. So the best place to request that someone put effort into maintaining a nightly build is Mozilla’s contact points. Don’t expect too much, though, because it is not trivial to maintain a snap and a nightly build is likely to require their (Mozillians’) manual input regularly.
FWIW there are currently two tracks for Firefox: latest and ESR; so it is expected that if there were a nightly release added it would be in a separate track, not a separate snap.