We have considered this for SE, factorissimo and now Space Age, and its complicated. Basically, all the mods that rely on multiple surfaces like that also depend on instant communication between them, which is impossible if they aren't on the same server.
We basically need to rewrite the mod to make it work.
We have https://mods.factorio.com/mod/universal_edges which allow you to run belts, pipes, trains etc between servers, which would facilitate something like factorissimo. For space age our plan is to use that to tile every world, so all the planets are infinitely scalable.
The new drop pod API means its also possible to have drop pods going across instances to hit platforms/landing pads on other instances, but nobody has picked up the project yet.
