City building/ management genres have all ways held my fancy. But for the most part the genre continues as a stand alone game. With in the current dry market. There has been a push towards Online play. But come on. Besides the enjoyment of creating working or dysfunctional city's. If no one can walk the streets as a citizen. Your missing out on an element of the game in my opinion. SimCity 4 did have MySim mode. But never followed game play into it's nature evolution. Dwarf Fortress allows for the creation of dwarfy city's and then follow up game play with in that world.
Sandbox RPG's often attempt to emulate an entire region of their setting. Allowing for vertical and horizontal character development. The missing element to a Role Playing game in my opinion is the Role Playing part. From my experience many times the in game character just becomes an avatar for the player them selves. I believe elements of The Sims 2 could help fill this hole. Creating greater Character immersion. By playing on the wants and needs of the in game character. Keep in mind any one who plays a sandbox has their own goals and interest. The counter balance to absolute autonomy is the continual need to satisfy the character their role playing. So the player can continue to move towards their personal goals for that character.
You may find people who do roll play with in an MMORPG hanging out in a tavern or local area of interest chatting. The only reason you would find a non role playing character or your average player in a tavern. Is if there was a vender or quest giver in that location. Now the idea in play is. What if the character was unhappy for what ever reason. Now if visiting the local tavern for what ever reason. Restored that characters happiness. Obviously the concept needs to be fleshed out beyond my example.
What kind of Fantasy RPG doesn't have "Dungeons". Going back to the management style of game play. I believe players who have an interest in running their own Dungeon are the antithesis to the current scripted grindy dungeon runs in current MMORPG's In my opinion it creates a new dynamic for the Player Vrs Player dynamic. Don't for get evil characters go to good inspired places and vice versa for the opposition.
Them park MMO's In their content driven investment are misappropriating their resources in my opinion. Now even games with shallow game play have been much improved. By giving the modding community the tools to shape and change aspects. It brings in greater longer life to any game in my opinion. Moddable aspects not only bring in greater imagination and resources. But all so increase commitment for that product. City of Heroes brings in the player community with their mission architect edition to the game. SimCity 4, The Sims 2, Spore, Civilization 4, RPG makers all show great examples of this. What may not be obvious to developers is. Creating user friendly tools to modd their games. Not in house only focus driven content.
Yes the waters have been dabbled in. Abandoned out of hand as well for some of the bad PR and Chaos it all generates. But if moddability is the first thought and not the last expansion to the game. Over sight and common sense limitations can be cleared at the forefront.
More then anything I believe these game playing styles need to be created and stand alone as good in their own regard. The defining factor and what sets it apart is they all tie into a MMOG in a persistent world. You would be creating a franchise that combines differing styles of games. Unified in a single persistent world. The current mainstream paradigm dead ends players behind content. No MMO shop can generate content fast enough to continuously satisfy their player base.