If it's not a ton of work, I'd say that it's a great idea to write a handler to accept any payment method. This would be good for people writing their own custom payment methods, although writing their own handlers might not be a bad idea. I think even if we have to force users to user a Credit card to buy a subscription, that's not so bad. But I like having the option there for PayPal as well and anything else that comes down the road.