Github actions for users registered to a website

My team wants to create an index repository for certain Python packages. Our goal is to have authors register their repo on our website (on our server) so that we can run CI tests on their package. Registered users would include their own tests and proper .yaml files in their repos.

I know github actions has releasd the Self Hosted Runners option which I think could work for us, however, according to github: 

Note: Currently, you can add self-hosted runners to repositories. The ability to add and manage self-hosted runners for an entire organization will come in a future release.

Would it be difficult to implement this registration based CI control and do I need to wait until the “entire organization”  functionality is released to do it?

Currently, the scope for a self-hosted runner is repository. Runner A in repo A could not be used in repo B.  RepoB needs to have its own self-hosted runner.   

>>Would it be difficult to implement this registration based CI control

I am not very clear about your scenario, is your workflow definite on the index repository ? Can you give an example to show why the self-hosted runner could work?