I've been committing code to the core WordPress codebase for 3 years, so while I'm not a PHP developer - I have some idea.
Perhaps one thing overlooked in the argument for fork vs new build is that there aren't a huge number of developers with the skills to make this happen who would do it entirely on an Open Source contribution basis as opposed to, say, a startup basis. Appealing to existing WordPress developers, businesses and users, as well as cutting down time to ship first working concept, are (in my mind) some important arguments in favour of a fork.
Perhaps one thing overlooked in the argument for fork vs new build is that there aren't a huge number of developers with the skills to make this happen who would do it entirely on an Open Source contribution basis as opposed to, say, a startup basis. Appealing to existing WordPress developers, businesses and users, as well as cutting down time to ship first working concept, are (in my mind) some important arguments in favour of a fork.