Anybody should be able pay up for the feature/support and it should be closed source until some threshold. That could take years or months depending on the interest/income. Eventually it will become open source. Otherwise, everybody will wait for someone to pay for the thing they want.

Obviously this needs to be worked up a bit so not to maintain N forks but it can work.

I think thays fine. Thats within the spirit of FOSS. The issue has always been companies demanding fixes because it affects their users, and those companies cant afford to wait. So now they can pay to have the devs spend a bit more time to get their fix out. This works

There are models out there like this. Look around the term "Fair Source" and I think you'll find them.