Ask HN: How would you turn a web agency into a SaaS for building websites?

This is largely a thought experiment. As someone who has worked at web agencies as a software engineer for years before, it has made me curious how they usually are content with not seeking beyond small/medium clients, as they seem to "plateau". Generally speaking, web agencies are not disruptive companies. I might seem them grow gradually over the years, from 10 to 100 people. And get higher dollar clients. But their growth is largely limited by their ability to acquire new clients.

How would you turn such an agency into a faster growing company that does SaaS for creating websites? The goal would be to be able to scale up acquiring customers, to the thousands, so basically you will need to automate the website building process. At some point the majority of your clients will use your online tools to create their website, rather than have custom work sourced out to your developers. What would be your strategy to change the company?