I don't really know how that is possible without giving people access to the entire game online. It would also make it so the people who made those mods would not be able to test play them in-game, meaning any mod released in that situation would be buggy and just a mess.
It would be a ton of work and effort and I just don't see the point. Very very few people would want to make mods that they could not use or test or do anything with.