If Volition did FS3 and it was a spiritual successor of FreeSpace 2 but with all of the usual associated upgrades then I think that would meet my expectations. That'd ensure that at least some of the folks who did the originals were still there and had the same concepts did the gameplay. Story and the rest is important but a good editor, a good engine, and solid gameplay would make FreeSpace sequel a top notch product.
FreeSpace was so good when it came out because it was the synthesized version of TIE Fighter and Wing Commander and blended all of the good things from past games, added mega huge capital ships, fast gameplay, and fantastic graphics. I WOULD be disappointed if a sequel went FreeLancer on us and did the mouse thing only...mouse is great and I'd expect it to be tweaked significantly to make it playable for everyone else in the FPS arena but the joystick is still where its at.