i gotto admit, i have had basicly no ingame experience with the [GC] so call me totally biased, as all my information is second hand. - however, by principle, i agree with chopper that faction equipment should be used over everything at reasonable terms.
the argument "but we get wasted otherwise" does not score at all, cause such an argument supports a "i get the best i can" attitude, which especially the official factions should not follow as a "good" RP example.
so my suggestion is to fly eagles of course and only fly red cats untill they have a valid alternative. - once they have, i d love to see them switch to the primary choice of the faction in RP terms. about weaponry.. i gotto say i have not the slightest idea about GC weapons. - they do have their own guns, from what i know - and they are not bad. - when you get down to it.... one can also pirate with an eagle and gaias angels, which are worse when its against transports ( or one can pirate "just as good as with codes or other borrowed equipment" )
if it is true that the GC mostly uses red cats and BDs... that IS a problem. its as bad as the LSF / Navy using buckshots, BDs using krakens, bounty hunters buying liberty battlecruisers, zoners flying corsair dreadnaughts. it does not fit the expected archetype.
however - i should be the last one to say that, as i am flying a corsair bomber with coladas as Clover ( its being switched next version.... but right now, it feels totally "wrong", too ) and i have asked officially for it, too. - ( still feels stupid ) - so when i write that, i gotto blame myself first. - but yea... the "better" alternative is to stick to what is expected from one to do. - a gaian should fly an eagle with gaians angels. a GC should fly an eagle with suncannons or whatever their weapons are. - very few members could maybe benefit from a weaponsdeal and use other guns... and even fewer could possibly fly another ship.
again all that is only based on what i read here as i had no experience with the GC ingame ever yet. ( that is partly, cause the profitable trades out of kusari are declared as contraband [ engine parts etc. ] and the diamond/niobium route, even if one uses the official route through frankfurt puts one into the same mold as the common "ooRP" player - so kusari is insignificant from my point of view )