Its tricky currently.

Hosting your own ChatGPT on your website is still not walk in the park + you pay for LLMs calls yourself. For heavy use you may end up spending dollars a day per user. So it could run to dozens of dollars per user per month. And you need your margin on top. If you end up charging for your bot more then ChatGPT Plus costs then what? Will compete with ChatGPT?

Alternative is to build service on proprietary data or services like your describe.

But provide is like Consensis as service in ChatGPT store, but user will need to login on your side. And there will be limits in free version, or they need to buy license for ChatGPT on your side which is cheap(only your margin)

And later you can invest in having a chatbot on your side with separate price.

I think this is strategy to go here.

And in the end your bot could provide better and more focused UX then ChatGPT for your nice use case. ChatGPT UI is only chat. No good integration with other UI paradigms.

Like say Microsoft Copilot for Office combines chat with Office tools so chat drives and integrated, which is better experience then just sitting in the chat. But still this requires a lot of work. Its expensive, so start with ChatGPT as low investment thing to test interest and demand before building complex things.