I know that when a cart is $0, FC does not send anything to the gateway, because gateways typically can't handle $0 transactions. But this could possibly result in collecting bad credit cards for subscriptions with future start dates.
Is it possible, or have you ever considered making it possible to send over an authorize only transaction for $1 or something in this case?
EDIT: never mind, I see that you have considered it based on the discussion here.
And less than a month ago. I'd delete this post instead of just editing it if it were possible.