After I've placed this deletion request, the maintainer of the package wine-staging-dev pushed a new commit adding the wine-nine patches in order to make it different from my package wine-staging-git, probably trying to escape from the deletion.
Even after this, I think that this package should be deleted. This would avoid confusion to users seeking the pure wine-staging VCS (development) package because the package names are quite the same and express the same thing.
The AUR wiki page says that the package name should express in what is it modified for. Quote from the wiki: "Exception to this strict rule may only be packages having extra features enabled and/or patches in comparison to the official ones. In such an occasion the pkgname should be different to express that difference."
If it would not be deleted, I think that it should be at least renamed to something else, like wine-staging-nine-git, or something similiar.