vRA8 disk and nic count

I am trying to create a vRA8 blueprint in which I can select either (1 or 2) NIC's and have the option to add additional drives to a blueprint.  Requests will be consumed through the API, not through Service Broker.

I was hoping the "count" property for the disks or network cards could help, but I get errors during deployment if I try to use them.

Is there another way to add a NIC or drive through an ABX action prior to allocation? Any recommendations are greatly appreciated.