I have many many thoughts on the topic. I will try to highlight some of them now.
Almost all modern games forget about the players that want to run games, and build ideas. Now is the time to bring that back.
The 3d action bar role playing game is great and is the standard that should remain. Multiple cameras, even locked cameras for isometric games should be possible.
In this age of massive multiplayer the game server should be capable of hosting hundreds of players. While modules may not be built with this in mind, the server software should be capable of doing it.
Standard rulesets should be developed, reviewed and reiterated by the community.
The art standards should be set by the community, forums and websites is great for this.
Multiple forms of combat should be allowed, both real time and turn based, tactical and other forms.
modern scripting with randomization and procedural generation.
The game engine and server should be capable of near perfect recreations of games such as
NWN1 and 2
Dragon Age 2
kotor 1& 1
world of warcraft mass effect
baulders gate
Planescape: torment
using turn based company even games like pokemon and xcom
Of course creating these in the game would take hours of writing scripted events, editing
UI could ( I am uncertain here) use html and css to create an interface quickly.
How would this be built? The community of course.
I suspect that many many people would be interested in a game such as this one. I think that the community could built it with the right management and vision behind it.