Trading XP versus combat XP is bad imbalanced, but money is worse. It is very, very hard to make money fighting, once supply costs and fuel costs are factored in. If you want to be a mogul you have to move a lot of trading.
One way to think of this problem is this: it is possible for a trader to make a billion, level up completely, and then construct a fleet out of nothing from "the ground up." Basically like a mogul buying a private army, sowing dragon's teeth that he bought. Not only is this fleet fully pimped out and awesome, but your fleet is 100% experienced without ever firing a shot. If you managed to pick up expert crew along the way, you even don't have to worry about training them.
Basically it is possible to become the baddest, most viciously powerful fleet in starsector trading 1 billion units of toilet paper. that is wrong, wrong wrong. Perhaps it should not be possible to gain combat experience from trading.
Maybe experience should be divided into channels somehow. Like, trading only counts toward industrial/logistical experience, while combat only counts toward combat and technology. Something like that
Basically it is possible to become the baddest, most viciously powerful fleet in starsector trading 1 billion units of toilet paper.
^really, that's ridiculous
edit: Another way to think of it, could boeing, Northrup, raytheon band together and kill a battalion of marines armed with small arms? No, they could not, because ultimately despite their wealth, logistics and experience the nerds that work for those corporations wouldn't know the first thing about hunting down and killing the marines, whereas the marines would very quickly destroy all the infrastructure that gives war corps their force projection. If that's too out there, how about this: could five East India Company galleons defeat a Man of War? Probably not.