Expanding on the concept of Galactic Civilizations, is the idea of Intergalactic Civilizations. You start off in your Home Galaxy and eventually expand to other galaxies. This would require a map of the galaxies (standard galaxy pics would do, and maps generated for each galaxy, though not loaded in memory, until you are in that galaxy, and only when the player is currently working in that galaxy.
Each galaxy has its own races, with abilities, agendas, etcetera. In the Lensmen series of books by E. E. "Doc" Smith, Ph.D., only 2 galaxies were used. Civilization was home based in the First Galaxy (this one), and Boskone was home based in the Second Galaxy (aka Lundmark's Nebula). I only bring this up to illustrate the concept.
This game may be required to be done for 64 bit Windows (post Vista will be 64 bit only).
You may encounters races from other galaxies in your home galaxy, and not always know they are not from your home galaxy.
Of course, there are many details to be worked out, and this would not be seen for some years. However, I think it is worthy of consideration for future developement.
All ideas are welcome, and this would be for Stardock to develop.