They're capped to 2GB? It's fairly safe to say there's no conceivable mod they can't run o.o The biggest mod I ever downloaded for Skyrim was 1.9GB to get more/more immersive NPCs. Any mods that size will likely be texture replacers, audio replacers or gigantic compilations of items (made up of meshes, textures and occasionally random bits like sound FX). Any mod along those lines can easily be split into smaller chunks. Saying that, the hi res texture packs are specifically for PC because we get shafted by lazy devs who CBA to give us better textures than they gave console peasants (not talking specifically Bethesda here, who absolutely gave us free hi res textures for Skyrim). Having hi res textures on console would be weird...they exist because PCs can handle them and consoles can't.
I noted the new login bits in-game. It's an interesting way of doing it. Obviously steam workshop wouldn't work and there's no other way on consoles to do it, so it's pretty sensible. Part of me feels a little uneasy at Bethesda getting so involved in the modding side of their game, after giving us the toolset that is. By its nature, modding is community run so having the devs get involved seems off somehow.