1. no

2.I don't know about scripts, but It isn't possible without them.

3.I guess, but the neutral planet would have to be a new planet type, otherwise all planets of that type would have the ability, neutral or not.

4.You can modify their attack strength, the duration between attacks, the types of ships attacking, and the amount of fleet supply that they can use in their attacks.

EDIT I'm assuming for #2 that you mean import it during the game. The answer is no, you can't.

Darn, there goes my idea.

The idea was a mod where you play as the Vasari loyalists, with their nemesis right behind them.  Worlds on one side of the map would disapear/be annihilated, along with anything in the gravity well.  It would slowly work it's way across.  Now, the plan would be to either have worlds disappear once they have been annihilated, or once you get to an exit wormhole save the game, exit, and run a script that moves all your guys in the exit wormhole to the start of a new map.

So it would be like a campaign, sort of.  You can have a fleet, and play scenarios people make, with your objective being get across.

I suppose it would be possible to do in one big map as well, but not nearly as cool.

I just like the idea of having a fleet on the run, trying to scrounge for resources as fast as possible so you can build a temporary base, rebuild some of your lost forces, and move on before you are destroyed.

Ha- I didn't even know that there was a BSG game.  Is it any good?