It is unfortunate.

Could you simply have a pay per game/month model? Giving the players the option to buy 1, 3, 5, 10 games/months at a time via an in game purchase?

Notifications then sent when approaching the time for renewal?

It would mean people and caught into subscriptions and pay for what they're happy to do so up front? Subscriptions for me always fall badly for time! Xbox live for instance is renewed the day before payday!