Thank you both, Neil Roberts and General Zhukov (love the name). It looks like the procurement person (who refused to let our attorneys speak to their attorneys to try to get to the bottom of the ask) finally had their boss come back to work. The boss contacted us and said we didn't need to incorporate a rate card into the subcontract anymore, and would we just please provide them pricing in response to their requested change orders. Well sure, of course we can do that.
But yes, unreasonable customer was unreasonable. Luckily, adult supervision intervened and everyone is now happy. Thanks to everyone who provided suggestions and sanity checks. I really thought I must be missing some double secret FAR provision somewhere.