Restrict Read access to thread forms content by group

We have a few use-cases where we would like to have data that is restricted to a staff rank on our forum, though where the rest of the information can be viewed by any logged in user. Thread forms look like the ideal use-case for this, but lack the ability to restrict viewing of a specific form field to a specific group(s).

I'm guessing there are plugins out there that could do this sort of thing, but from experience on other forum suites they tend to be a bit lacking and we've had issues with users being able to bypass it. Having something native to the forum suite that could accommodate this would be really good.