Just an improvement perhaps.
In the trade window, you can see the merchant's gold when buying and your own when selling. That makes little sense, because you don't know what your budget is for buying, and, vice versa, you don't know how much more the merchant can buy from you. Although seeing your money increase when selling is kinda useful, I'd still prefer to know how much money I have left when buying. I guess it would be best if we could see both at the same time?