How can a PhD in Machine Learning and AI help you in a life out of Academia?
Working at your startup

One thing for sure is that, if you want to start a company (a startup), you should not be afraid of being overqualified, since you will be "the boss" and there is no one to classify you as such.

Working in the industry

While being overqualified sometimes (perhaps, even, often) applies to positions in the industry, a Ph.D. graduate is highly unlikely to be considered as such in ML/AI domain, where it is often a requirement for most positions.

Working for other people's startup

Even though most startups generally don't care about degrees, those, working in ML/AI-related domains, will be happy to consider and hire a good Ph.D. graduate for the obvious reason: due to relatively high complexity of the required ML/AI-related subject domain expertise.

P.S. Please note that my answer addresses only your concern of being overqualified, but does not touch a larger question of feasibility of your plan, factors to consider in decision making and so on. However, it implicitly suggests that this one of possible routes to achieve your goal (whether it's the best or the optimal one, depends on a lot of factors, including your personal circumstances).