I may not have been clear in my previous two posts but at this point unless someone in the community decides to investigate further if stacks can work with variables, it won't be changed. Now, if no one cares enough about this to test (and learn in the process), so be it, it'll remain on the to-do list until we get to it.
Yeah, there seems to be technical limitations related to this request. There might be solutions, but they might be more confusing than just keeping things the way they are.
Perhaps a more reasonable request would be to create dialogue options for vendors of the most common ingredients. So that the pc can for example,
ask to buy "10 hides" (or a spoken number), and then a script can dump them into your inventory as a separate stack.
Its probably not the neatest solution to this problem. But it is a short term solution that's probably
good enough to address the general spirit of what people are discussing here.