(Edit: My comment sounds more negative than intended. The author has already spent some time and effort on the codebase and that's commendable and should be encouraged. I was trying to point out that others have also had the same ideas and thoughts, and spent efforts towards it and so a collaboration with other like-minded projects would be beneficial to all.)
There are already decent hard ( e.g. http://www.palemoon.org/ ) and soft ( e.g. GNU IceCat - https://www.gnu.org/software/gnuzilla , LibreWolf - https://librewolf.net/ , Tor Browser - https://download.torproject.org/ etc. see https://alternativeto.net/browse/all/?tag=gecko-based for more) forks of Firefox available. Better to contribute to them than start another fork. In fact, Tor Browser (without Tor), actually comes pretty close to being a "bare" Firefox browser.
(Edit: My comment sounds more negative than intended. The author has already spent some time and effort on the codebase and that's commendable and should be encouraged. I was trying to point out that others have also had the same ideas and thoughts, and spent efforts towards it and so a collaboration with other like-minded projects would be beneficial to all.)