The currently existing Patreon integration enables you to give access to specific games if a user is a patron of yours with a minimum $ amount of a pledge.
As far as I understand, this is not connected to cookies in any way. It only uses the OAuth2 workflow to validate the user has an active pledge on Patreon. If the pledge is found and fulfills the minimum $ requirement, a key for the game is added to users itchio account.
We use this to distribute Patreon-only builds to our patrons. As Subscribestar supports OAuth2 as well, it'd be neat to have this functionality available for Subscribestar as well! :)