Hi,
My name is Pontus and I work for a web development company called Geborek Solutions. We specialize in building tailored E-commerce sites based on either Woocommerce or Magento.
I would love to build you a digital downloads shop on Wordpress/Woocommerce. This is the platform Louis CK built his webpage on. It has full support for digital downloads, both as DLC and for streaming. I can extend it to support most common payment gateways rather easily.
The way I would go about this is to create an easy demo site for you to have a look at, with just a default design, just so you get a feel for the platform, how to upload videos, how it works to download them and such. I can have this up in a couple hours if you contact me, and if you find it to your liking we can have a more thorough chat about how to go about the rest of the project.
Best regards
Pontus