i would like to see crafting, factions and good economy, that's it.
crafting its self explanatory, making everything from food and cloth to weapons (or even building for factions).
good "economy" means no super god like class that can do everything, you must be depend on everyone else, for example you need the crafters to fix your equipment(equipment need to decay) or to make something better than the generic stuff in the market.
you need the "fighter" to defend the faction crafters and in the battlefield you must to cooperate with other classes (ranged,close) and support classes(medics, engineers?)
if the game will not encourage team play, it will end like many others where you basically can do everything yourself no need for team work and after time you go to the next game (see fallen earth)
since there is no chance in a MMO for "actions and consequences" meaning every save the town and the world, the only real palce to see progression is in factions, meaning the stronger you get you can improve your faction base have some special faction tabard everyone will recognize and hopefully faction war