OpenOffice -> LibreOffice fork and transition seems particularly instructive here:
A huge, user-facing organization? ✅
Managing a bunch of connected, complex software projects? ✅
With a huge amount of documentation (wiki, etc) for both developers and users? ✅
Deeply engaged in open standards debates that affect everyone? ✅
It's not about the individual software projects. It's about all of the above. LibreOffice came out stronger after the fork. So could a fork of Mozilla.
I hear there's a bunch of Mozillians available out there these days though...
The bigger problem is organization and funding. People need to eat and pay rent. And Yahoos and Googles of this world will not be interested in contributing, even if their contributions were to be accepted.
NLnet might be a good place to start looking for funding:
Server run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!