Is this possible?

[Shyatic]

Just wondering if you can create a system that integrates with IPB or uses its login auth system as like a plugin, that will let you manage a subscription based service (a bit beyond what the subscription manager does) like a magazine or online game. Let's say I want to use "coupon codes" that can extend a subscription. Let's say I want people to be able to pre-pay 6 months, or a year with a discount. Let's say they go month to month. I want them to be promoted into a 'paid users' group if they are currently subscribed, and demoted out if they are not so they can't see some forums.

How would I start going to do this? What method or avenue is there? I am not asking anybody to WRITE it for me, but at least to get a start on an API or the documentation to figure out how to link it all in and make a really customized addon for IPB that works for my needs.

Thanks!