Any attempt to make something new from the fs2 code will be severely limited by the requirement of CD's. This game is hard to find and only getting scarcer.
In the source I see a lot of DEMO preprocessor code, but the comments mention that the demo has branched off from the main fs2 code (rendering the demo code we see obsolete). I have not tried, but I doubt its possible to compile the demo exe.
The only good solution I can see is to re-create resources from scratch. This is the only way a complete working program could be distributed.
Or maybe Volition, Interplay (or whoever makes decisions), would "release" the resource files. The game is not for sale on Interplay's online store, though FS1 is, oddly enough.