If it's for an entire company, then it's easy enough to compile your own copy of firefox that accepts extensions signed with the company signature rather than mozilla.
Respectfully disagree - having to rebuild each time patches come out, on multiple OSes and versions, which have a patch to allow unsigned extensions is a massively more time expensive than developing a browser extension, and requires extra knowledge on the behalf of the persons responsible
Luckily it's not necessary: you can still enable a flag in ESR releases that allow installation of unsigned add-ons, so that solves it for company-internal tools.
