A great read and a lot of good points here, and I agree with just about everything. One note I'd like to add about the Trading problem is that prices on goods will change as you are buying them. You're right about about how traders should focus on buying wholesale, but currently the game won't allow this because when you buy in bulk the price of goods increases before you even finish the transaction!
Normally when you buy in bulk the price of goods will decrease, the seller would rather sell 100 units now than slowly over time. But in Bannerlord the seller hikes up the price as you buy more, hurting your profit margins. And the same applies when you sell in bulk too; the price of goods decreases if you sell in large quantities. At the very least, the price of goods shouldn't change until after the transaction.