To be fair, I'm trying to turn it into a public product since I think the use-case isn't very niche.
I've recently started building https://responsebrain.com where I can add all my blog articles and automatically let ChatGPT generate responses to questions about my other product https://webtoapp.design
It's a pretty basic setup with a knowledge base you can feed anything you want (your blog articles, help center etc.). That gets put into a vector database and then I pass the related knowledge pieces to GPT along with the question.
I know there's lots of similar products out there, but none of them seem to allow manual editing of your knowledge base and they all seem to be focused on creating chatbots. I've adjusted the prompts to work best for e-mails.