I'm really doubtful about this approach. We discussed in #60083 that crawlers can vary by input format, so that one factory service or interface cannot rule them all.
The need for a factory is to support functions you wrote. If that's The use case for having a service, then we'd need to have support for functions. Without a use case in core, there's no need for any design pattern overhead.
Then, assuming function is really the use case, what about an approach where the functions themselves are provided as a service (or a collection/container of services)? Then one would inject this "functions provider" and then instantiate the exact implementation they need: eg new JsonCrawler($data, $functionsProvider)

I really like the approach of functions provider being the service instead of the crawler or a factory. I'm having a look at it!

Let's close this one. I'll definitely implement the functions provider mechanism, but I won't work on this one before the crawler is compliant with the RFC test suite. 🙂