Not sure if it has been mentioned before, but I think it would be nice to put in an "Amount to purchase" box for items instead of having to buy them 1 at a time when someone would like to purchase multiples of the same item.
 
Just a thought, but I'm quite sure there would be a lot of people in favor of it. Thanks for listening.

I don't believe that will get done anywhere in a short future. I would suggest quicker fix for this issue: make purchase gump appear again after purchase so player at least can repeatedly click "Buy".

Meanwile, when you need to buy lots of same type of item like magical cloth deed or weapon level deed, just record a quick macro in Razor and run it in loop. I recorded full process starting from clicking on stone and ended with buying item and it worked very well for me.