I haven't looked at the source too deeply yet to investigate how you implement the fork, but you state that it's a fork of Firefox, how do you plan to integrate fixes from Firefox (security, etc)?

It's implemented as a set of patches + new files for net new files I add myself, then to build it, the firefox source is downloaded and patched automatically - so bumping the underlying firefox version is generally very easy.

I'm currently actually tracking the firefox beta channel because the frequent small updates are so easy to do.