The amount of time and effort expended on this must be immense. Would it have been feasible at the time to sponsor having these changes pushed into mainline?
Many if not most of these patches have been attempted to be mainlined. Either they were not considered of acceptable quality, considered too similar to other features (ex: Binder in Android) or rejected for other reasons (ex: Google's Fibers and SwitchTo).
If you have a patch that saves significant resources, improves important performance metrics or unblocks hardware that does those things you don't care if upstream will take the patches or wait for them to decide if they will. You simply start using the patches ASAP and reap the benefits, then you continue trying to upstream the patches to reduce the maintenance burden.
If you have a patch that saves significant resources, improves important performance metrics or unblocks hardware that does those things you don't care if upstream will take the patches or wait for them to decide if they will. You simply start using the patches ASAP and reap the benefits, then you continue trying to upstream the patches to reduce the maintenance burden.