The biggest problem with MMO's is the "Massive" part of the design. The player is always the hero: the exceptional one that can get things done. Except that in an MMO, you aren't exceptional. EVERYONE else is just as badass as you. Because there are literally thousands of heroes stomping around doing exactly the same thing, the world CAN'T change or the newest heroes wouldn't have anything to do.
I propose that someone make a "Moderately-Multiplayer" game with a max of a couple dozen to a couple hundred people on a server. If localized servers aren't in the business plan, then for a monthly subscription, let someone rent a virtual server and control the logins on it so that they can play with friends and ban incompatible players. Let the players be real heroes and not "just another hero". You get this feel in some games like in the Red Dead series, but it's not a persistent world.
So I like where your design is going, sunandshadow. It's something I'd certainly like to play. I just think that there should be a limit to how many players can realistically and practically exist in one continuum.
What if the point of the MMO wasn't to be the most badass, or for that matter a hero? I see an MMO more as people who want to adventure in the same virtual world. Having great and meaningful gameplay experiences isn't really about being the best fighter on the server, or the richest person on the server. Your gameplay experience, your story, should be important because it's yours, and shaped by your choices, not because you're inherently special compared to everyone else in the world. Here let me copy& paste you a thing from my gamesprout page for my design:
My goal in designing WildWright is to create a gameplay experience which feels like the player has entered an interactive novel. Specifically a fantasy romance novel, or at least a fantasy novel with optional romance content. I'm really tired of the traditional "hero" role in RPGs which is all about becoming the most badass fighter in the world. There's nothing wrong with that goal, but it shouldn't be the only goal open for gamers to pursue in a virtual world. Instead I want to create a gameplay experience which is more like the typical 'heroine' role in a romance novel.
So, for those not familiar with the genre, what is the heroine role of a romance novel like? Romance novels are closely related to the "bildungsroman" story archetype - that means a story which is about a young person becoming an adult and finding a place they can fit comfortably into adult society, which often includes finding a mate. This is quite compatible with the basic activities of an RPG, such as leveling up, earning money, obtaining a house or other property, gaining abilities and fame, and exploring the world. Self-development is in fact an underdeveloped theme in many RPGs, and by bringing this theme front-and-center WildWright should be able to have a really strong combination of story and gameplay because the two will conceptually support each other.
In addition to the bildungsroman role of young adult finding a satisfying adult position in society, a romance novel heroine is often a problem solver. She may not be able to directly tackle her own major problems, but helps those around her (NPCs). This builds relationships between the heroine and other characters, who in turn often repay her with help for her own difficulties. Again, this is all completely compatible with RPG gameplay; there are many great games, from the Harvest Moon series and Azure Dreams, which are dating-sim hybrids, to mainstream games like Skyrim and WoW, where the player can carry out quests or solve dialogue puzzles to strategically build friendships with NPCs for various reputation rewards.
Another thing romance novel heroines often do is investigate mysteries. The problem of a romance novel is not usually a big monster that can be attacked with straightforward violence, but instead a tangled, unbalanced situation which is a puzzle the heroine must investigate and use persuasion, psychology, and ingenuity to solve. This is really ideal for a story-heavy RPG because it's a more fresh and meaty reason to send the player traveling here and there than yet another mercenary job to lower the population of some monster or gather X drops from said monster. Totally compatible with RPG gameplay such as exploring, giving items and information to NPCs, and again solving dialogue puzzles. And a romance heroine can use force but she uses it strategically, not as an indiscriminate way of life; for example she hunts a particular type of monster because she wants its antlers to craft glue needed for a more elaborate project.
Finally, romance novel heroines don't act as part of a "dungeon party", they mostly "play solo". I think the market of MMOs which are friendly to an introverted play style is really underdeveloped. A lot of people don't seem to grasp why someone who wants to mostly play alone would want to play an MMO. This is a result of not understanding the benefits introverts and others get out of more passive socialization, such as doing the same activity as another nearby player. You don't have to do the activity breathing down each others' necks to feel a sense of community. Creative people in particular get a lot of benefit from doing their solo creation in a shared world where other players can comment on their efforts, and the creator can see what has already been created by others as a challenge to answer with their own future creations. Having other people in a world to talk to and trade with is key to making a player feel like their time spent in the world really means something. So, WildWright will be very solo-friendly; there will be instanced dungeons for small parties of friends, but all such dungeons will also have a single-player mode. There will not be specialized healer and tank classes which are slow or difficult to play with in solo PvE. (Having pre-determined classes would also be incompatible with WildWright's theme of personal evolution; instead players can seek out abilities they want to add to their character's repertoire, and the game will recognize a player's functional class by the abilities that player uses the most and the activities that player spends the most time on within the game.