Today it is only possible to exclude sites from the font page - I would also like to have an "I

This theme is "bull’s eye" for me, for the multisite. As a part of the multisite I am also trying to set up a site showing only certain sites for the org. I represent ("system owner") .
We do have a lot of areas that we would like to promote and it would be really nice to be able to use the “Network” theme for this presentation. The problem now is that every new site also pops up in this presentation…
Would really appreciate feedback if it, one way or the other, could be considered to incorporate a “include only” type of list.
Alternatively if there is another theme which “looks the same” / gives the same presentation…?
Best regards
Erik Johansen