About it being possible to jump to another system within mission - that's possible! In fact, that'd be easier than the jumping to another part of the same level.
The way you could arrange it, is to offer a new campaign feature with the code. (You've got training, and loops, right? Easy. You've also got stuff coming from one mission to another in FS1, right?)
All you need to do is follow a sequence using 3 missions:
1. missiona
2.subspacelevel (can last for any wished amount of time.)
3. missionb
Take away the breifing sequences, and possibly arrange a new form of the subspace level(might be harder right here) to where once you reach the end of a tunnel, it would load the next mission. At the start of the next mission, you'd go through a transparent image of a subspace portal already going at a velocity, and BOOM! you're there.
You could easily do these effects by removing the briefing screens, and going straight into loading the missions without them. To create the end of the tunnel subspace effect, simply put a large image(similiar to the nebula effect) that the player can reach. Once it is reached, load the next mission! (This can be done through some new SEXP's.)
Okay, so it's rather more complicated than I originally thought, but it can be done.
I think the things that everyone wants mostly revolve around a lot of the same stuff:
-Enterable planets, ships, stations, etc.
-Player autopilot.
-Able to put the player on any wing wished.
-Improved computer AI.
-No limit on the travel distance.
-Limited nebulaes
-Animated textures
-Lights
-New SEXP's<----I think just some stuff to go with the new features. The mission design system is great, IMO.)
-Better limits. Unlimited ships, events, messages, etc in FRED2
-Improved graphics/interface/hardware extensiveness.
We should work toward the stuff that's most critical and would make the biggest impact first. Then move onto stuff like capital ship missle bays, hatches that open, close, and release weapons, etc. Those extras can come later.
But does anyone really truely understand the fact that with this information, we could improve the engine to its full extent, and effectively create an FS3?