As a customer, I'd be concerned about longevity and data loss if/when you go away or pivot. Knowing that I could export my data, and re-implement my own backend using your open data standard if needed, would go a long way to easing my concerns.
Most customers won't go through the effort to build their own solution, and for those few that do you can easily out-perform with service, experience, and expertise.
You could even offer bespoke integration services...