stock – Bypass inventory validation on a non-MSI store

For the last couple of weeks, I have been trying to find a way where a product is a backorder only on the main stores while being able to be freely ordered one store in particular. We cannot use MSI as it interferes with our operations on the fulfillment side, so we can only use the global catalog.

I know that there is only one global quantity for all products outside of MSI (referring to this question), so my only other option (that I am aware of) is bypassing the quantity and stock check that the Catalog module uses when it adds a product to the cart (referring to the Validate function in the file QuantityValidator.php) or (answered in a different question) use setIsSuperMode to elevate the product above any validation functions? What is the correct way to approach this problem without using MSI for a solution?