5.4 was released already. We're planning for 5.5 to allow the explicit configuration of sorting fields: the feature is almost ready and we hope to publish a beta release this week.

But this will not strictly check at runtime: for backwards compatibility, we'll only issue a warning when a sorting field is used which was not previously annotated to be a valid sort field. We will though expose it as metadata, so you should be able to query the metadata and have your application check/verify for it in advance.