I honestly don't know if I could play a Bethesda game more than a month without mods.
Obviously an MMORPG won't have any playermade equipment, quests, NPCs, areas etc..
It would be tons of work for Bethesda to implement, bugcheck and balance out, in addition to that every player needs all mod data installed to be able to play with others. Would be the largest game ever in file size.