We're using Chargebee in our app since Stripe is a bit too simple when it comes to subscriptions.

I'm thinking something like Chargebee/Recurly should be open-source, with a gitlab model and with charts like chartmogul.com built-in as well to centralize all subscriptions info/reporting. I'm not sure whether the open-source aspect would be enough to convince enough people to use it, but it would convince me at least.