I've talked to a nginx product manager and he's told me changes that are specific to one customer are unlikely to be accepted.
Also in our implementation we took some shortcuts so it may not be suitable for upstream as is anyway
I think it'd be great if more companies released their own 'opinionated' versions that update with their infrastructure. Like if I wanted to host a OpenStreetMaps tiling server hypothetically using some features cloudflare has in their nginx builds. Makes it easy for white-hats to test, too.
IIRC I've been intersted in HPACK for small http responses where the headers are larger than the body, but if I wanted to use the HPACK patch I have to re-impliment it every time an update comes out that modifies the file.