Good idea, but for this particular situation, it doesn't work due to the members who use this site.
Thanks for explaining a little more and of course whatever you want to do is fine and great.
I will say a couple of things more but please just ignore them if they don't help.
One is that all major online services seem to do automatic monthly charging... and that applies from Porn sites/channels to Sky to AOL to just about everything everywhere. The reason they choose that system is of course obvious, it makes them vastly more money.
I know of one firm that actually closed down its online services and with just some basic pages and two part time staff left watching them even months later they still had hundreds of thousands of members paying them automatically each month.
The concept of telling existing customers to go away each month seems really odd.. and constantly needing to renew something will of course drive away most people in time. Even if you feel one month is often enough for what you offer you can still use the auto renewal system and simply explain to people they can cancel anytime they want via PayPal.
I'm having to guess at what the problem may be... maybe it is a security one and you feel people will not want to be associated with your site on a long term basis... the moment they charge to a card or make a payment of any type it goes on record though and they are perhaps still associated really.
Anyway, you know all the details and whatever you want to do is fine... I just feel strongly that a lot of folks bring in vastly less income than they could by not using subscriptions fully.
As v1 of Xen comes to the end of its time as the current version and with v2 due as the next serious version release you may feel it is the time to base your business on a v1 add-on, and to start paying for it, and to pay for it each year from now on and so on.... I just wonder about it and so wanted to give an alternative view.
I hope whatever you do works out.
Steve