Great question. We did just launch a marketplace for apps, but it may take some creative thinking on how to utilize that for the goal you stated. You can read about the marketplace launch here:
While we do not offer a platform in which we charge customers for apps on your behalf, or directly expose any way for you to charge customers to use it, it is absolutely possible to introduce apps to our marketplace in which the offered application is mutually beneficial for it’s creator and our customer. Two great examples of this right now are cPanel and Plesk. With cPanel, you are required to purchase a license for their software to function. For Plesk, they offer a limited free license and an upgrade path. Both being very popular software that a lot of people do pay for, these were strong value adds to our marketplace, and mutually beneficial for their creators as well as our customers.
I hope that provides some perspective on our current iteration of the marketplace :)