Just a small change to luxury traders to accept high end finished foodstuffs, such as cheesewheels, pies and alcohols. Depending on the complexity of the item whether it be in ingredients or steps to make, it receives a higher or lower price; e.g. a pure onion pie would go for a single gear, or not be accepted at all, while a pie with meats and several different vegetables or rarer fruits would give a larger payout. The same concept can be applied to alcohol, should we ever get more variety in the future. The more base ciders and spirits selling for low or not at all, while aged wines and champagnes would sell high.
You might be thinking "why shouldn't this go under the food trader category?" My answer would be; the food trader is all about selling much more base items you'd see commoners consume, such as simple ingredients and breads or tools. The more high end 'luxurious' foods which would correspond more towards the rich and decadent, in my opinion, belong with the luxury trader.