I've been wandering around, doing the merchant thing, and it's been going well so far. I have more than 15 thousand thaler, which seems like a lot, but isn't quite enough for the best equipment. However, that's not really a problem because I've reached a point of power where it's unlikely that my wealth will go down over time.
It turned out not to be too difficult. All it really took was me gathering 15 mercenary troops and then not chasing the various bandits, looters, and deserters when they ran away from me. I'd almost consider it a flaw in the game, but I'm not sure that being a pure merchant is actually an intended mode of play. You don't get experience points from trading goods, for example. And there doesn't appear to be any way to parlay a trading career into favor with nobles or landed property. Also, the AI doesn't seem to know what to do with merchant characters. At one point, I wandered up to a castle under siege and the besiegers just let me through and then the castle garrison opened the gates for me. Obviously, at least one of the three of us doesn't understand how sieges are supposed to work.
It' clear at some point I'm going to have to engage with the game on its own terms - pick a faction to associate with, gather up a mercenary army, and attempt to win renown on the field of battle. However, before that happens, I hope to be ridiculously rich. I'm worried that trade income won't scale up as I grow in wealth, but if it does, I'll probably be doing that for quite some time.
A more realistic prediction is that I will somehow burn out and wind up just doing whatever easy thing is closest to my current location, going from one time-wasting bit of nonsense to another.
Only time will tell.