We can put them all in the same OC as you suggest (with the different BGs as outgoing distributors), which should work correctly as in you set as available incoming all the variants for the products you’re supplying that week, and then make sure the outgoing FC only has the bulk ones, and then each buying group can change their variant availability.
The problem is just the dates - that each order cycle has one open and close date, and the buying groups need to close before FC so that they can aggregate / adjust their orders to meet FC bulk amounts.
If we did it this way, you will still only see / receive the orders for FC wholesale (provided we make sure that you are not ‘managing’ the BG’s), not those for each BG’s customers
re. how the orders get to FC, the current proposal is that once BG has worked out their totals etc they place the order manually into FC order cycle. There is more discussion of options around this in that first mega-response that I did - Bulk and group buying - wishlist (section: BG places order with FC wholesale)