I have seen and studied this pre-view "Approved Customer List" ( 10.0.0.43 ) which I find very interesting, what I think could be useful is to also have the option to "exclude" certain products\variants and not just include. With the current function, if I want to exclude some items\variants for a customer, I should create a group with ALL the items\variants and then go and remove what I want to exclude. In addition to being inconvenient, this would force you to maintain the group every time new products\variants are created that otherwise the customer would not see.