It would almost be cool to see "FS1 junker fleets"... It typically takes a long time to recycle old warships. Fighters go much faster to the recycling mill, but if there's no GTVA, there's been a serious problem. Thus we can conclude that... if this isn't too far post-Capella, a good deal of the technology will have probably been relatively stagnant in development.
Recall that bombers like the Athena got put into storage during Reconstruction. If the GTVA storage depots remained relatively intact during the Second Incursion, you might succeed in bringing back the old birds in a credible way (unlike "Twilight," one of the poorer campaigns I've ever played and its use of the Apollo) with storytelling. Regardless of the date, due to the nature of the environment you're suggesting, this campaign might really succeed with pirates. And if you've got a mash of really old warships and fighters in there, you could make for a sort of dark, "primitive" environment which would definately make for a distinctive campaign. Heck, throw a random militia/pirate wing of GTF Angels in there... you'd never expect it.