The best ship in there is definitely the Barghest.
Can your OC GS take on a cruiser by itself?
That's what I thought.
The only advantage the GS has is that it's better vs heavy fighters and things like the BHG GS. But pirates don't need to fight enemy fighters... they're supposed to be fighting transports. And if you aren't pirating...
Srsly, the lawfuls in Liberty appreciate being able to fly small ships without backup now and then... and the Upholder isn't exactly a Bergelmir either. Also, believe it or not, but there are actually people behind most of those Guardians, Avengers, and Liberators! And despite what the [Cartel] seems to believe, you *can* kill a Liberator with less than three Outcast gunships. No, I'm serious, this is their stated opinion, I wish I still had the link for the screenshot...
EDIT: Not calling you a capwhore, and it's quite likely we actually fly bombers about as much- (although I'm starting to like Heavy Fighters) just saying that when people bring out entire squadrons of gunboats there is no option except to swarm with heavy capital ships- and while caps can be great fun, a lot of people prefer fighters.... and fighters vs missileboats isn't exactly "fun". Spontaneous groupings are fun and nice, but if you get the chance go for the balanced fleet- that way everyone has something they can do.