Let her rust! I think the Gunboat would make a great older ship, like say it was a mainstay in the Republic fleet that has been totally superseded by the TIE Bomber or its predecessors, but there are still a lot of them in use by smaller organizations, pirates etc. You would have to strip down its capabilities from the TG games (like 8 torps, no ions, flies like a brick) to make it work in that role, but it seems to me that SW can always use more crappy older ships flying around, especially ones that do look somewhat recognizably SW. That would give neutral forces a bomber (the only other option I can think of would be Y-wings, which, as the mainstay of the rich Alliance, are probably too pricey for pirates) and it's way better looking than any Prequel fighter IMO.
Why defang it? It seems like the majority of EU ships are all about one-upping their trilogy counterparts, but if you look at the Alliance at Yavin (described as "well equipped" by at least one high ranking Imperial), they had basically 30 fighters to send against the Death Star, and it's not like there was any reason to hold anything back. So I say give us more of the rusty, outdated stuff to make the "low end" Y-wings and TIE fighters look like the elite fighting machines they are supposed to be.
As for the model, I think if you beef it up a bit and shorten the nose and wings it will look very nice!

The Blastboat just sucks, Zahn or no.