I would love to see an intermediate trader between the 5000 and barge, the gap is far too wide and their should be something inbetween...
One crazy idea I had one night was a Heavy Very Large Train Freighter/Fighter (with good firepower only once detached). It can detach from its cargo like an Artic lorry (once detached diverting max power to guns/speed become avaliable only) to fight off raiders then joint up again the raders are defeated.