I realise this could be a niche Use Case, but have you tried to see if the existing iPad version will work unaltered in iPad emulation mode (as many apps seem to do) on the Vision Pro? If it would that could mean you do not need to provide a Vision Pro specific version until you decide there is sufficient demand to justify the effort.
At the moment the App Store seems to be set up so that it cannot even be loaded as an iPad compatible app. I would be willing to test this out if you do not have a Vision Pro of your own to test it on.