Adding per-recipient custom headers in a custom hook?

Hello all-

I'm working on a custom hook, and I have some headers will vary depending on the recipient. 

Is there a way to do per-recipient header edits in a custom hook?

I see how it's done in add_forwarding_header_edits_per_recip, but that's very specific, with no way of bringing in headers that could have been added in a "checks" custom hook, for example.

Any thoughts?


Tom