My open source work is a hobby. If you want to give me some money for something I would do anyway, I probably won't say no. Or if you and people like you paid me enough consistently that I could quit my day job and focus completely on my OSS projects, then I would probably do that. But even for $1k an hour I don't know that I would want to deal with contractual obligations for my hobby project.
Of course that isn't the case for all projects, but you can't always assume that the maintainer is willing to accept payment if you are willing to give it.
I think a better model might be to have consultant companies that employee people to fulfill bounties on various projects, and possibly handle building and distributing custom forks if the upstream maintainer is unresponsive (or just takes longer than the customer wants) or doesn't want the change upstream.
Of course that isn't the case for all projects, but you can't always assume that the maintainer is willing to accept payment if you are willing to give it.
I think a better model might be to have consultant companies that employee people to fulfill bounties on various projects, and possibly handle building and distributing custom forks if the upstream maintainer is unresponsive (or just takes longer than the customer wants) or doesn't want the change upstream.