So give them template buttons for different marketing tasks. 1. Create messaging. 2. Create branding. 3. Create market positioning. etc.
The user presses a button, enters in product, target market, budget, competitors, or whatever, and a GPT works out the rest for you. AutoGPT and AgentGPT show what can be done nowadays, and so this is a natural vertical extension of those tools.
In your demo, most people wouldn't really understand a persona, or how to craft features, benefits etc. Nor should they, that's what your tool is for surely?
Again, really like the idea, but not sure the implementation will deliver the kind of results you're looking for.