IFMU writes “ and concurrently help the FAA rewrite Part 29.”.
Aye, there’s the rub: early in my SA career I received a short brief on the best way forward with the FAA, which was in short: Never go into any FAA meeting and ask them to help you with a solution to a problem, rather, enter the meeting WITH the solution, and then explain in detail how/why it meets Part 29. The idea behind this approach is simple and in the case of the FBW question, particularly applicable: the FAA obviously does not have the expertise on the subject, but the applicant/design team does.
Now, having said that, I have met and worked with a few absolutely excellent FAA aviators and a couple of engineers. But where the current FAA staff is on the FBW subject is clearly indicated by the absence of Part 29 certification standards, plus the Advisory Circular indicating how the applicant should go about proving they meet the standard, some 20+ years after FBW helicopters were airborne. One can understand the use of special conditions, as for something unique, like the rear seat controls in the CH-54 Skycrane, but whole aircraft?
But as you say, IFMU, the applicant company must be ready for the possible consequences, e.g., a difference of opinion by the FAA re some aspect of the control system. A financial gamble with unknown odds. I’d imagine that the AW-609 folks have established some useful precedents, but I’d also bet that the 92 FBW system looks different, thus the precedents may not hold across the board.