I think 2nd Gen X ships are impossible to ballance, but 1st Gen X ships are plain dull. In any case, I've made a shiplist that I intended for Dynaverse play that greatly expands the 2nd Gen X ships and tries to make some sort of ballence between them.
I had to add a few models, because I've added ships to cover all the move bases between 0.33 and 1.00, plus dreadnaughts. I've done things like gave the Mirak more engine and fewer missles. I had to completely redo the fighterlist, and assign year appropriate fighters, so the AI's wouldn't be a push-over.
If you would like to see my shiplist, contact me, the package is 36.5 MB, without a readme. I'll need to cut out some models before it's ready for prime time.