Well, it is a mess but it is a curable mess. I wish I was your Mortgage Broker I would be on the phone with GMAC working something out. So basically Mr. X signed an open deed. That's an odd ball way of doing things. An open deed is not valid until enacted as you say and recorded. So Mr. X could sell the property again. Now granted he would commit fraud with the relo company if he did.
Someone needs to have a conference call to get everyone on the same page. This isn't a matter of GMAC does not want to do the deal, it is a matter of they don't like the process. So there is some fix to it. I would get the closing attorney, the head of closing for GMAC, and the attorney for the RELO company on the phone and work it out.
Off the top of my head there are three work outs that GMAC would accept or should accept. The relo company taking their place in the chain of title, GMAC being reasonable about a LEGITIMATE relocation company having POA, or (the most complicated and likely scenario) the relocation company putting the deed in escrow with the closing attorney in exchange for a release of funds signed by Mr. X given to the closing attorney. That way, Mr. X can feel comfortable that he is not committing fraud against the relo company, the relo company will know they will get the disbursement from the closing attorney, GMAC will have Mr. X signing the documents because he is officially on title, and you don't give a shit who signs as long as title insurance covers the transaction!
What idiots. Who is handling your mortgage? Your next step is to start informing various people of their liabilities if they do not deliver. But don't start threatening yet.