I'm curious if it's useful! How do others try to solve use cases like this of mapping data between docs or strictly controlling LLM edits?

Can this be used with gemini 2 flash while OCR'ing pdfs?

It doesn't deal with images at all, but depending on what you're doing it might be useful in cleaning up the OCR text, e.g. asking LLMs to fix errors and then filtering the diffs.