MMORPG's are frequently disappointing. It's important for me to occasionally remember this when I have the urge to play one. I made this list to both point out to myself that the game (It's WoW) I would be returning to does not have any of these things, and would therefore be unsatisfying to me. Also it's fun to make a list of things that would be included in my ideal MMO.
1. You may have and control a single character at a time. No alts.
Alts have always bugged me. It takes you out of the focus of a game to have too many perspectives. It would be far cooler to make a game that had a flexible class system that allowed you to go on an adventure to learn the fighting styles of the mountain folk and incorporate that into your character instead of starting an alt.
2. Gold you keep in a bank and gold you have on you are two separate things.
A small pet peeve, it would be important in the system I'm thinking of because...
3. Stealing from other players would be possible.
Because it's fun to be kept on your toes. Game's aren't real, so they should never be dull. Being able to legitimately pickpocket someone if you were skilled enough? Super cool. Being able to thwart a would-be thief? Double cool.
4. Where you began the game would be important.
Not just in a "I like starting in forests" kind of way. It would give you a set of skills and possibly a fighting style that gave variety to the world without everything having to be about race. Travel to other places could be difficult. In fact, different continents could be whole different servers. Remember, this doesn't have to be possible, it's just for fun.
5. Picking a race does not mean picking a side.
Like, c'mon. It's way more fun if you have to actually pick who your friends are. If you want pre-selected enemies. Join a faction that has some. Also, PVP would always be enabled.
6. Factions would mean something.
Allying yourself with a faction would grant you new gear, abilities, spells, knowledge about the world, and of course- opposing factions.
7. You are who you are assumed to be.
Wearing a specific outfit, emblem, disguise or simply a suit of armor says a lot about you from a small distance. As does your appearance. People are much more likely to be on edge around someone who smells like dried blood and horse shit, carrying the severed heads of several local bounties. Dress and Hygene would affect NPC AND player reactions, because there would be no HUD display of identity automatically available.
8. The world must change.
When something dies, it dies. Enemies don't re-spawn unless it makes sense for them to. Dragons don't keep dropping a few nick-knacks at time. They drop the whole horde of treasure ONCE. And people fight about who gets what for a long, long time.
9. Magic is scary.
Spells are found, stolen or learned as an apprentice to a more powerful sorcerer. Magic takes a toll on you. Marks you. Being able to use it effectively would take proper training and sacrifice.
10. Magic items you find in a cave are therefore twice as scary.
The safest and most reliable method of obtaining items would be through a local craftsperson. Magic items would be really powerful and unique. Wielding a magic sword of intense power without the proper resistances or precautions could lead to you losing control of your character and it becoming a servant to the weapon/armor/etc. How fucking cool would it be to have to kill a boss that used to be your character?
11. Combat needs to be interesting.
Combat would not be standardized. Different "schools" based around weapons and philosophies would be a significant choice in playing a character. Movement rate would be a key statistic. Being over-laden would make you slower in and out of combat. Honestly I could write a whole post on just this, so I'll just say that MMO combat is not as interesting as it could be.
12. Death should be a real threat.
Death would be permanent. There would be a number of ways to protect against it, but ultimately a character who dies must start over. Their body (assuming it was not destroyed) and possessions would continue to exist, and could be recovered- by literally anyone who finds it, including wandering monsters and NPC's.
13. Balance is not the key.
There should not be a clear cut path. Stacking obscure fire resistance gear can be a perfectly good solution. Sometimes you need two characters to kill one character. Imbalance leads to creative problem solving.