I would like to second the request. Just today on Zalera i needed some Aldgoat leather, and there was ONE person selling them. A stack of 41 pieces for a total of 12.300 gil. I can't afford prices like that, so not being able to buy units out of stacks really is ruining my progress here and just costing me WAY more money than I would need to spend otherwise.
So yes, please fix this.