Awesome, I'm glad you were looking into this and all of that sounds great.
I'm not sure how an upward cap per stall would play out, but from my experience with v2.9 each stall has an insignificant cost to produce and land requirement to where having to build 6 or 7 of them for each resource I'm overproducing wouldn't impose any meaningful cost on me as a player at any relevant point. I think there needs to be something meaningfully imposed on the player to entice or dissuade them from building more stalls before requiring more stalls becomes a thing. For example if more stalls increased the severity and frequency of bandit raids, as a player I would naturally begin to cut back on production and stockpiling (Because honestly it's more stockpiling than profit if you're producing more than 300 of a resource a day) to line up with what my defenses could handle.