I'd love to see a Freespace mod for SoaSE. You have three races in that game, three races here, all three being somewhat similar to another.
Though, it would be great if we could blend the two, where you could pilot a bomber or strike craft in SoaSE, or even one of the guns on a ship / turret. Don't think we can do that though with the tools we have.
And yes, Freespace 2 runs in XP with the Source Code Project. The goodies you get there make the game A LOT more enjoyable visually! Just look it all up in the Hard Light forums.