This is an excellent project but it can lead to a can of worms. At the least, please add a checkbox to make sure that the poster who is charging SATS for the uploaded content is allowed to do so, so that other people's copyrighted materials are not downloaded and made available for SATS collection at your expense. I know that you will have the signed keys for the person who will use your site to upload such materials, but anyone can create keys, including bots that will post and mine SATS on your site. So, somehow, you need to create a mechanism on your site that states that people are uploading either their own work or they are not stealing and selling stuff from others. Somehow those checks and balances need to be ensured.