Well you gotta be careful about the powerplant of the GS. It's as small as the GS is agile. One basic missile takes half of the powerplant's capacity. I'd suggest Razor or Pulse Cannon, however I haven't tested them.
I did notice though, that there are two neat looking ports on either side of the ship's nose.
How is this for a radical suggestion: Take away the front 'forward cannon' turret, and put a torp slot on either side where those ports are on the nose.
Energy-based guns like the SNAC would have to be barred due to balance reasons - but it would be interesting to see a gunboat acting as a torpedo platform instead of having a 'forward gun'.
Be even better if the Gaians developed an EMP torpedo to go with the Nova (reverse hull/shield damage and hey presto!).
Radical I know, But hey have a think about it...
If I could get in-principle support I would be willing to have a go and develop it.