From what I've seen, the Starcraft 2 engine is ridiculously flexible. Just for example, within the user interface of the ship, in the cantina, there's an arcade game that's an old-school shmup built entirely within the in-game engine. It might be suitable for something like a Crusader game--with the added advantage of outside environments being simple. I'll be taking a look at it in the near future and reporting back.