i see both sides of the isles, and i like both sides and agree. co-op would be super uber, but again, this game is meant to be a single player not a co-op. Bethesda is a massive company, if the players wanted a co-op option bethesda would ocnsider it and even possibly release a beta for the skyrimites to test and rate. i personally think it would be freaking awesome if a tank could blast/hack his way into the middle of a fight and an assassin pick people off of the sides. or distract while the other recoupes and rejoins and vice-versa.
Instead of split screen how about 2-different consoles just hooked up, i forget what thats called, but i think it would be awesome. i think the online idea would be a bust, cuz of the same reason of M.A.G. just to many people on a server, one with a bad connection could ruin it for the rest; also just to much data on a server, kinda like the WoW server style, it owuld have to be broken up so many times and a cap of people per server and individual "load" areas or just a distance cap (like in runescape, once you reach a certain distance the world has to refresh, reloading your map around you, "forgetting" a part of the map that no longer affects you, but is still active, just not on your computer.) but this would ruin the beauty of SKyrim, standing in the marshes and looking across the marsh on a clear day to see a dragon scouring a mountain top across the map.
one possible idea would be dungeons or quests that could be available in a que that characters of any type could gather to attempt, of course it would adjusted by the lvl's and size of the party, and some set dungeons/quests for standard difficulty. And even customizable dungeons (not sure about quests though, but im sure it workable) with a list of things to change and like daggerfell(or was it arena) the dungeon charcteristics itself is random, just not the content.
This is an idea from Oblivion, There could be an area; pvp or co-op(fighting along-side a player against incredibly difficult monsters with limited gear, the more limited the gear, the higher the reward, be it rank and/or gold. Another setting in the Arena would be PvP + monsters, so that each player has to decide which is the harder foe (ie, if the monster is harder than the person, then they would attack the monster then as soon as the monster is slain make a turn on the player, and vice-versa).Survival mode(non-stop waves).
There could also be other online activities as well as fighting, one would be horse racing, with bets of in-game gold. Even though this is contradictory of dragon lore, there could be dragon-riding battles, both where the dragon controls itself and the player arches/mages(melee would be impossible untill they crash land(which could launch you and even kill you)) or for more advance controls, te player controls the dragon and attacks the other player.
Another idea would be deer/elk hunts, (I don't think this would be very exciting for all, but and option all together) with each deer/elk having a different body mass/rack size and shape. And you have to track it and hunt it, all the dangers included, sabers, wolves, maybe a draogn, depending on the players chosen diffculty. The group would be on the same map, same server, hunting the same animal. the best part would be that all the dangerous animals could kill your target before you.
Ha, this got me excited, hahahhahaha