I imagine there is money to be made. The big hurdle is initial development of the customer's deployment app and the proxy/security location. But once those two work, a one time purchase or subscription could start bringing in revenue.

I foresee scalability and bandwidth to be a hurdle if you have 35,000 users running on average 10 apps. This setup would automatically double needed bandwidth by delivering content on the web and communication through VPN. Spitballing, but caching (if possible) would help, video like jellyfin would hurt pretty bad, but then again that sort of isn't selfhosting anymore.

Oh, and it'd have to be cheaper then just buying a VPS. It's a potential business, but trapped in a tight box of competition. Keep in mind your #1 client, those who rely on corporate solutions, would need a reason to switch and understand what they are doing. My parents aren't going to jump ship from their walled garden because AI stole their eclipse photos.