My ideal MMOrpg (lets be clear on the emphasis

)
Firstly, the game would be created, from the very start, with a viewpoint of a 'tool' for creating content. That would be the primary goal, not for the players but for future developers. Something that can be very easily updated, into which it is relatively easy to import new textures, models, data, missions, monsters etc.
The tool would also be designed for in game guides/GMs to use, much like a broader-scope NWN GM tool. They could use it to spawn or despawn monsters, posess NPCs or opponents and talk 'in voice' with the players. This would provide the playerbase with the 'thrill' of human opponents, without overboard PvP and allow for the constant creation of new content by the people on the ground.
Within that framework you would then create the game.
The game would have the following...
Character Creation
No classes. You would create your character using a set number of points to determne their statistics and skills. Some of these skills everyone would have a base chance at, others not. Breakpoints in these skills might give access to certain special, skill-derived abilities. There would be enough points to be pretty competent but an insanely high expertise in one particular skill, making you a master of it, would leave you scant for points towards other things (the cost to raise a skill would go higher the higher you bought it).
The character creation would give you massive control over your character's appearance with facial detail as good as Ryzom's and a massive starting wardrobe of gear/equipment/armour etc for you to rummage through and get your appearance 'just right'. You could even, potentially, customise the details and colours of each piece to get it right for you.
Character Advancement
There would be little to no 'experience points' as we now define them. If for example the statistics and skills were percentile based (1-100) then you might, perhaps, get +1 point per month of play and that would be all. Some statistics might be able to be raised by 'working out' in game, but this would be a necessarily tedious grind. 'Buffing up' would affect the build of your character.
Advancement would be gleaned through acquiring wealth, acquiring fame and reputation and so on, depending on the world.
PvP
This may surprise you but it would be full and free at all times. However, the penalty for murder, outside of any in game conflicts due to plotline or events, would be SEVERE. A 'murderer' flag and the instant hostility of any guards etc in the area. If you get caught, you go to prison (almost a sub game) where you must remain until your wanted timer (caused by the murder or other crimes) runs down. If you can avoid getting caught, more power to you. Murderers would also get a reward assigned to their death/capture depending on their wanted level. The maximum penalty might be 100 days (real) in prison, though depending on the game there might be ways to lower this, like good behaviour. Honestly, I would expect the prison to become a PvP sub zone, soaking up all the PvPers since they'd probably shank each other all the time in prison, thereby increasing their sentences.
Permanent Death
Each time you die there would be a chance of permanent death, increasing slowly over time. First time 1%, second time 2% and so on. Permanent death coupled with the relative evenness of player characters (the ability for anyone to get lucky in defending themselves) should help discourage willy-nilly PvP, as would the jail. Eventually though, you'd be SOL and die. There would be the opportunity to get memorials and, depending on the game, very complicated quests for resurrections might be possible. When you die you turn up at the nearest hospital or equivalent.
Combat
You would have an array of combat actions and the combat would be fairly swift and fairly deadly, relying more on skill and equipment than the level type of 'uberness'. There would be no hitpoint system but something more similar to Deus Ex's wound/injury metre. How badly you were wounded would depend how badly you were hit, by what, what armour you had and how tough your character was. An arm wound might preclude you from using two handed weapons or carrying as much, a leg wound might make you stagger, two might make you crawl, and so on.
Crafting Etc
There would be huge and massive depth to this. Skill level would determine quite how many bells and whistles you got with more and more options for customisation the higher you got.
For example, someone with Tailor 10% (out of 100) might be able to make some very basic brown clothing, at 20% someone would get more colours and styles. At 30% still more and some designs etc to pick from a wide selection, or to customise or upload their own.
Those are all generalities, the scope of the game.
A particular individual one I'd do?
I'd like a horror game, a zombie apocalypse. You'd start in a settlement, barricaded and protected from the surrounding nightmare but in order to get weapons, ammunition and so on you'd have to go beyond the walls. More zombies every day would come to the city, trying to batter down the walls. Maybe there are other settlements, maybe you could barricade yourself in, can you trust other survivors?
When you died, you'd rise as another zombie and play as that until you died again, then it would be new character time...
There'd be more to it, but that's the gist
