I believe I've brought it up before, but I think the traders should stop carrying leather and fur armor, because that doesn't make sense to bring from abroad, and rather bring metal armor which is hard to come by.
Traders are mostly good for the occasional valuables they bring, as well as having a reasonable chance to bring quality weapons (but not tools, for some reason).
Beasts of burden would allow traders to carry more wares, although the vessels vikings used probably weren't suitable for horses, so it would probably be ahistorical (on the other hand, their names are more gothic than scandinavian, and the pre Hanseatic League ships might have had a better cargo capacity).
An additional complication is that traders would have to have some mechanism to trade directly from their beasts' inventories (but possibly by not actually carrying any trade goods themselves: that's what the beasts are for, after all).