That eliminates the risk of any angry customer with disabled ink.
However, the new problem is that most customers would rather have the current situation pay as you go situation than pay up front.
Id be dammed if I pay full price for a product AND a subscription. If it is a 50% discount (as advertised), the customer is still looking at 3 cartridges before they break even.
Solution: non-refundable first month, make it greater than cost of first ink cartridge. Risk removed.