Can I ask why you want to cut out the AC+ monthly payment, but are ok making what's essentially the sum of those payments one-time?
I get that a true pro-rated amount would be slightly less, given upfront AC+ is cheaper than sum of monthly payments... But that aside, this feels a little bit like forcing a "cut to monthly subscriptions" in your life, but not actually cutting out the expense? Like, if it's more a psychology / budgeting thing, you could just make a "lump-sum payment" of the remaining monthly payments (that would get you to the 2yr mark) into a savings account, and then just draw from that savings account every month to pay for the AC+ payment?
I understand if there are other reasons you want to do this...