crowdfunding bounties amongst users of OSS for features they'd like to see is a very interesting concept indeed and could help. however, it may also be a double-edged sword for the maintainers (ex users might feel 'entitled' with their requests now that money is involved, and this might happen on issues that are not part of the maintainers' roadmap).
we've been asked about this before, we don't yet understand all the dynamics here fully and refrained from developing, but it's a feature we can ship easily. we're holding back until a project explicitly agrees to have crowdfunded bounties in their repo and users who are ready to crowdfund it. happy to hear more feedback on this and continue the conversation!