By passing this on to Mozilla and discontinuing Tor Browser, you're going to inherit the innumerable issues in their code base. Wouldn't it be easier to hard-fork and create a simple browser with minimal overhead? It doesn't have to be loaded with features. Just minimalist and private.
Some anti-features that come to my attention off the top of my head:
* Biometric login (as of FF60)
* Dumb PR Stunts like Mr. Robot
* Telemetry
* Balrog (Analytics and browser fingerprinting on AmazonS3)
* Social API
* VR sensors
* DRM
* Google Chrome (large contract Mozilla has with them as they backport this into IPC)
* CloudFlare DNS (Department of Homeland Security partner and Tor arch-enemy)
etc...