I'm so very pleased to see that the engine is being created so thoughtfully. I think some people are forgetting, or simply don't realize, that a game engine isn't nessecarily an FPS engine, or an RPG engine. A game engine is only limited by what its creators designed it to handle.
If a game is an arrangment of parts, then the game engine represents all of the available parts to build the game. Even if two games use the exact same set of parts, if they are put together differently you have 2 unique games (basicly games of the same genre with similar mechanics). The Unreal engine is primarily comprised of parts to create realistic graphics and close up action oriented real time games with physics. These games tend to be first person shooters because those are the games that are the easiest to create with the available parts. But RPGs and other real time games can be made with it.
If the fine folks at Stardock create an engine thats capable of handling multiple game genres, then more power to them. Not only does it mean, that modders wiill have alot of freedom with what they create, but it also saves Stardock alot of time and money with future projects.