Adding the ability to buy sub "vouchers"
Imagine being able to buy 10 sub-vouchers in one go, which you can use like the prime sub, by checking a checkbox. This would mean that there would only be one bundled payment instead of having multiple payments.
You could maybe even use the vouchers to gift a sub.
The possible advantage from my point of view is that you can pay for all your subscriptions at the same time, which would make
This could maybe even come with a discount as there should be less money transfer fees.
Going even further: You could have an autobuy option for the vouchers, so you have e.g. 10subs a month available.