Or you could just treat issues as another kind of patch, which anyone could send by email or pull request, and maintainers could accept, reject, modify, clarify

Or you could just treat issues as another kind of patch, which anyone could send by email or pull request, and maintainers could accept, reject, modify, clarify, etc. It's true this would be harder for less technical users to submit problems. You might want a way to map anything submitted by Github Issues or the like into patches, though you could also do it manually.