I really liked early Square titles because I only played them with my friends. They were single player, yes, but they were also party- and turn-based. Holding the controller and pushing the buttons didn't matter as much as deciding where to go, what to do, or which spell to use. I played through dozens of NES, SNES, and PS1 titles only touching the controller half the time. The rise of 3d real time RPGs has spelled the death of the party-based RPG, and with it the death of playing an RPG with friends. MMORPGs and games like Neverwinter Nights seek to recreate that dynamic, but with a laserlike focus on a single character for each player.
Why not bring back the party as the central focus of the RPG? Why not recreate that "sitting on the couch and taking about the game" dynamic in an online setting? Why not make a modern RPG with these old-school trappings?
The major win for this style of play was that all players didn't have to be present for the party to advance. I could play FFT all Saturday at my friend's house, and he could level up our characters during the week. Having all players present is a major problem for those of us reading this bboard who have tried playing a game together. Instead of designing a character, players in online RPGs should design a party. Ownership of the party would be divided among several players.
Each player could be responsible for one or more characters. Players could share control fluidly; a dinner break shouldn't break the party. At the simplest, a game designer could let every player in the party control every character, and let the players themselves work out the methods of cooperating. I'm sure there are more complicated ways of sharing control that may work even better.
A party would be a unit of hierarchy between a guild and a group. Like a guild, players would not change their party membership lightly or often. Like a group, only a handful of players would belong to a party, probably only one per character in the party. You could still have groups of parties and guilds of parties, as well.
Many high level guilds already organize their characters this way, though the facilities for doing so are very limited. I think a lot of people could enjoy this type of interaction if the game design explicitly took it into account.