@enricostn I’m sure you are also concerned by that discussion, @paroga also you might be interested to discuss.
Today there are ways to manage that in the OFN, but as you say @carchrae this needs to be improved to really meet the buying groups needs. @enricostn needs that for his Katuma project in Spain, maybe you could work together on spec? 
I think though this could work with the variant option, like if a wholesaler have a product which is Apple Case, the BG can createa variant and only propose those variants of the product to their members so sell Apple by kg.
The piece of feature missing I think is the correspondence between the variants, this is connected to that issue: Quantities "on hand" adaptating when variants are a sub-product of the main product
So we need to be able to say that a variant is a “sub-product” of a given product so that the quantity available for the product adapt, and so that you can also adapt to the buying group case here to have full cases sold.