Personally, I would like to play TESV with a friend. I love the idea of teaming up against the big baddies, or even very high levelled caves, that are generally too high for single players (still doable at high levels, of course - TES is naturally a single player series) as long as the game is completely created FOR single player, without co-op in mind, I don't see how it could go wrong at all. There would be a bit of complication with mods, of course, but it's the price of mods, and it's worth it. Players could download mods from the ther player's list, and download the load order, they could deactivate any mods, or mods could be ignored, and only create a few errors, and be up to the players to fix 'em.
I wouldn't like a versus mode, myself, but tbh, it would hardly take any effort compared to a lot of suggesions you see around the suggestion thread, and I would rather see it than some of the stuff there...
If Bethesda ever made an MMO, I would think that they'd put aside a completely different part of the company for it. I doubt they would just shut out what got them where they are just like that. In this case, it wouldn't bother me, as long as it doesn't interfere with standard TES.