I'm not totally happy with my three level 70 characters in WoW: the mage would need a lot of reputation that the first two characters already grinded. Some reputations are now much harder to get, because nobody visits normal dungeons any more. Others are simply boring, and I'm so not up for killing the same mob over and over for the third time. So I was wondering why some things, like reputation, aren't shared between alts. And why can't alts for example enchant or disenchant each other's gear, which for that purpose could be put in a shared bank slot. Overall I find WoW treats alts too much like completely separate characters, and not enough like different aspects of the same player.
That made me think of the various Pokemon RPGs on the Nintendo. In them you play a boy who is a trainer of Pokemons. And in combat you play the various Pokemons. So part of the character development takes place for the trainer, and part of the character development applies only to the particular Pokemon that fought. And that is something I'd like to see more in MMORPGs: Part of what you do in the game counts for the whole account, e.g. reputation, and part of the rewards only apply to the character you're currently playing, like xp and levels. Right now the only account-wide thing is gold, which can be more easily transferred between characters of the same account than between strangers.
Another interesting improvement would be making quest rewards and epic crafted items "bind on account" instead of bind on pickup. Why can't my mage tailor make crafted epic robes for my priest? And how often did you do a quest where you couldn't use any of the quest rewards, but an alt of yours would have loved them. I'd keep dungeon drops bind on pickup, because making those bind on account would only encourage ninjalooting. But I don't see why crafted and quested items need to bound to the character instead of the account.