Currently, the Sonata input schema is a standard JSON-schema. The UI leverages all the features of this JSON schema using react-jsonschema-form. So features like validating using a regexp, selecting from a list of values, defining types like numbers etc are supported.

However, there are features that the standard json-schema does not support:

1. The user should be able to populate dropdowns from backstage entities.

2. the user should be able to dynamically define validaiton. It should be possible to define an API that will accept the input and return whether or not it's valid

3. The user should be able to provide custom components for different types.