Jump Hole Generator
First, simply make it quite expensive and only mountable on certain ships. This isn't much help though. The real balancing comes through the actual use of the generator.
I would prefer a jump hole generator over a hyperdrive for a number of reasons. With a jump hole generator, wingmates could follow you to the system you are jumping to. It would also allow enemies to follow you as well. This helps with the balancing.
A generated jump hole would have to collapse after a certain amount of time...say 15 seconds? This keeps systems from getting filled with jumpholes. I think jumpholes should also be destructable, almost like using a cruise disruptor. The problem with this is that whoever is being pursued would be able to turn around and destroy the jumphole behind them. Therefore, I propose that there be a special piece of equipment not unlike a missile launcher that could collapse a jump hole. To make it fair though, it will only mount on the hardpoint for the jump hole generator. That way, a ship could have either a jump hole generator or a hole collapsor (sic?).
It would also only be fair to be able to create a jump hole to a system you have been to before. You could create an interface with the map in Freelancer. When you click on a spot in a system, an option would be to create a hole in that spot. Of course, if you create a jump hole inside a planet or a sun or a radioactive area would be quite bad for the pilot so the pilot creating the hole would have to have some knowledge of the system.
Another way of increasing fairness would be the time it takes to generate a hole. An instant jump hole generator would be quite unfair. I think that to create the hole, engines must be cut and weapons must go offline. I think shields should stay up, we can't leave the ship completely defenseless. But it would leave you as a sitting duck. Basically, it couldn't be used in combat unless you had some wingmen covering you.
Some problems:
The first and most major problem I can see is that it may not be possible to create a jump hole out of thin air. It just may be impossible from the game's point of view. One way of counteracting this could possibly be to have jump holes in every point in space throughout the system and just have them be invisible and rather undefined. The jump hole generator could perhaps edit the data for the nearest invisible hole and activate it. This also may not be possible. You guys would know better than I would.
Secondly, you would essentially be creating two jump holes in two different systems simultaneously. When one closes the other must close as well. The other problem would whether or not to make the hole in the other system dockable. Would the jump hole created in the other system lead to the system your leaving? This may be a nightmare to work out in multiplayer but I think it may not be as big of a problem in single player.
OK, opinions? Maybe this is already an extensively covered topic somewhere. I just didn't have the time to read through everything but nothing quite like what I'm talking about came up when I searched. Thanks for taking the time to read this rather long post.
-dalix