I read that email and felt like Amazon have just given a massive 2 fingers to their customers.
Being of sound mind, i'd never use a debit card online.
I have a Barclaycard (visa) linked to my Barclays account. My barclaycard balance shows in my banking app, i can pay over money from savings to bill etc.I've had the same current account and barclaycard account for thrity years, and to suit Amazon, they want me to change it now 
I've had amazon prime since it opened in the UK and was a very early amazon customer, but this just won't work for me.
This shows quite a whopping level of contempt for their customers.