What I want to see is a fully developed d20 Modern CRPG with a tool system. Make a near future cyberpunk styled campaign setting, but have the toolset be able to do other styles as well. Here's the kicker, have the game be able to use NWN2 models, scripts, and the rules system and vice versa that way if you have both games installed you have huge amount of resources to develop modules in.
Yes, make it stand alone, but have it act as an "expansion" in sharing resources.