This is a great idea and a desktop app is the right fit for a product that aims to give sovereignty to the user. The app should be able to generate HTML files and then upload them to one of the supported providers (netlify, private vps, etc), and at the same time it should also support a list of DNS providers so that it can point the user owned domain to the correct hosting provider. That way the user maintains ownership of the domain and can switch hosting providers at the click of a button.
This means that you as the app developer would be out of the loop and couldn't easily sell the user out. You would only be there to provide updates, include more providers etc.
edit: reading the description of you software better, I think this is what you are going for. The thing you haven't added yet is domain management.
Thanks for reading my idea! Yes i think you understand the concept pretty well. I'd like to be 'out of the loop' as much as possible: Write what you like! As for domain management, I think my app could help with that but I suspect that since it's a once-off thing, a couple of tutorial videos for how to do it yourself with amazon or azure would hopefully do the trick.
This means that you as the app developer would be out of the loop and couldn't easily sell the user out. You would only be there to provide updates, include more providers etc.
edit: reading the description of you software better, I think this is what you are going for. The thing you haven't added yet is domain management.