Technically, it would be possible to run the games themselves in a sandbox. I mean, games are a class of software packages that really don’t need to have access to my system as a whole.

That’s really more on Microsoft or Apple or Valve or the Linux distro maintainers to work out, though – I don’t think that mod sites are in a position to do a lot about that, even if mods exacerbate the need for such a thing.