no GB guns - cause even large fighters look totally distorted with gunboat guns ( - they are simply too big ). the idea of a light junker bomber with a GB gun instead of a SN was made earlier.... and failed due to that fact.
a ship of a fighter size looks rediculous with a GB gun. - and even if its often said that the 4.84 BHG gunship is smaller than a fighter.... it is in fact not ( its larger and still looks stupid with most GB guns ).
making a unique gun? - possible.... but not probable.
the most useful idea would be to do what the Death Scythe can do. - one CD and one CD/torp mount ... along with reasonable stats and a HF powerplant ( to fire a razor ) - it would be a real light bomber without the ability to fire a nova / supernova - but the ability to fire a 20k dam gun - and a train CD if needed.
a heavy torp mounted gun wouldn t be too far off, when it was transformed to a mech on a planetary surface, where you might need heavy artilery, cause i guess that stationary installations on a planets surface are much more hardened than ships in space.
but this was also discussed already... and if one house gets a useful 1xCD/1xCD/torp mount HF/VHF - everyone wants one. ...