Allow quantity changes on subscription renewal orders
I would LOVE to be able to use subscriptions as a way to set an entitlement to "x" amount of something over the subscription period. This isn't my example, but I think it's a reasonable representative example of what I need to do...think about music (song) downloads. A subscription that let you download up to 25 or 50 or whatever quantity of songs per period (let's use a month for this example). For the 1st month, they pay whatever quantity they chose times a unit price per song (let's say $0.10/song). So for 50 songs it's $5.00 for the 1st month. But after the 1st month, they only pay for what they actually use. So in Month 2, if they only download 17, they would only be charged 17 * $0.10 = $1.70. Similarly, in Month 3, if they only downloaded 29 songs, they would be charged 29 * $0.10 = $2.90.
But their subscription would be for "Up to 50" per month. In essence, the quantity on the original/initial order becomes a sort of an entitlement of how many songs they can have per month...and using variable subscriptions, they could upgrade / downgrade their account...but still only be charged each month (after Month 1) for their ACTUAL usage.
In the scenario I have in mind, there is a separate system that manages the "downloads", but that system could be queried at renewal time for the actual usage (i.e., quantity) to be charge for that month.
What say ye?