It would be best if AMD shipped at least some CPUs without this bit in the
first place and released the code/specs for all critical components
(including critical graphics pieces for working 3d, video, etc).
What you propose might be at least be an acceptable temporary solution. Would
it work though I don't know. We need someone who is more knowledgeable about
the code and the problem to look into it. I'm guessing that if it was just a
matter of leaving it out then it would have been done already. There is
probably something more to it. If there isn't then we need to ask, wait, and
push for it to be released in this manor.
There may be another issue here that is unknown. For instance maybe AMD is
not willing to put in the time and effort to release it as such. The solution
might be then to get a third party to do the work under NDA. At which point
AMD could release, maintain, document, etc the code in a way that was
acceptable to free software proponents.
