I think having some kind of SSO login barrier that allows a website to turn into a portal would be amazing and not so complicated to integrate. Currently there is just memberships that allows for a login portal.
Use case: giving special discounts and special pricing to members who sign up with an account (for ecom purposes).
Use case: using SSO to grant new access to menu options once logged in. Valuable for payed blogs as memberships.
Use case (my case) : Similar to above. One of my clients has this issue where she only sells her products as a supplier, not a retailer. so when her customers or salon technicians find out they can get her products on a public site at wholesale prices, she has to get into contact with the person and deal with the problem manually.
Current workaround for her is we're using an approval form just for salon owners that will trigger an automation and send special supplier store link only (we use order forms) once approved by her.