Nothing mods the storyline at the moment... so your out of luck on that point. You can play the same story again, but with added ships/weapons etc - but not a new storyline.

As for the mods - there are plenty that add star systems etc. The thing you want to do is go for "broke" first (as in play some of the largest and most comprehensive mods that edit nearly everything) - or go for some that add just one or two new things to the game - and explore.

There are up and downsides to each:

Large mod
Advantage: You get it all in one go, new systems, new commodities, new guns, new ships
Disadvantage: What will you try next? You have just gotten everything - you won't really play anything else once bored, as they won't offer much new... except slightly different variations on names/types and layouts.

Small mods
Advantage: You can try tons of them, and they will stil retain individualities. You can fully appreciate some ideas without them being lost or taken for granted in the melee of a large mod.
Disadvantage: You may quickly bore of their individual changes, or crave more.

People will recommend their favourite mods to you - but that doesn't reflect your way of playing. Only go for ones others recommend IF they can offer a decent and descriptive breakdown of the mod, what its about, what it does - what features it includes, why are these features good, what balance you get etc. If they just list a name - or say its the best ever.... then they simply are going off their personal preference and NOT accounting for what you may be after.

You know, if you want a big mod, but still have the basics of the game, Epislon by Nova Desgin is one of the best big mods that i have ever tried. You should try that. It is open singleplayer, multiplayer. Good luck!

go look for tie universe mods their alot of fun changes the battle ship ships and adds acouple of nomad systems that are fun mainly order shipyards.


No Guts
---------------
No Glory

I have tried a lot of mods and one of the ones that I have always gone back to is the eveolutions mod. It is a large mod that has tons of comodities and a smarter AI. Another good mod is any by Starfyre (correct spelling), it is not my style because of the asteroid fields and the weapon effects are a little over the top . Nova design does some really good mods and I have had fun with them. but Eveolutions is one mod that all others are mesured aginst. ( this is something I have noticed on other posts in theses forums). But in all honesty you should just check many of them out and see which one suites your play style best. Each mod has a discription with it and most of them are pritty discriptive of what the mod contains. So good luck out there and its good to see someone who still looves this game.

Blessed Be to all those that still dream of the flight to the stars.