[wdihuwuhidhuw]

Canceling an item is fully within a customers right - they cant suspect fraud if the item doesn't deliver anymore.

Yes that is quite true and may be one of the pros of your post, as users are indistinguishable from genuine customers trying to cancel their orders.
To my knowledge, only such customer service exists at Amazon where you can cancel an item after it has been shipped.
l am fairly new but it seems to me that people have been accustomed to how lenient they are in general.
I'm sure it would be laughable to request other companies to cancel your order while it's in transit and you would have to end up refusing delivery or returning the item.

A question regarding the aftermath, is there a chance of users being billed after it is noticed that the cancelled item was in fact delivered? Wouldn't this render an account useless as payment methods would then have to be disconnected?