Imagine this scenario:

Parent Company -> Child A
Parent Company -> Child B
Parent Company -> Child C

Now for products I have child-specific products, global products, and multi-company products. Example:

Product A = Child A (child-specific)
Product B = Child A, Child B, Child C (global)
Product C = Child A, Child B (multi-company)
Product C != Child C

Products A & B are easy to set up, but how do I configure Product C? It needs to be available for Companies A & B but not available to Company C. If I set it to global it is available to all, not to some.