Yes, the type certificate process is not flawed. The engine is. How did you read my post as critical of the process?
The HP/IP structure is having problems because the engine has new demands on it, and the test process was based on insufficient information. I notice you have relented on your position of "stub pipe duff, let's move on" ??
This iteration of the 900 is expected to produce higher power at higher RPM, an invitation for gremlins to pounce. Vibration, Lightweight, and new components in a design that doesn't share enough of its predecessor's systems to qualify as a "Sister", a follow on, or a family member perhaps.
An "apparently improved" HP/IP structure?? Have you some idea what that would mean, and do you know how long that would take and that it would disable current authorization? Added weight, augmented milling and dimensions, new testing, etc. etc. Stop flailing at windmills.
Contra Rotation, higher discrepant RPM in the same box, and a "Standard" Oil System. Throw in LP vulnerabilities (via "standard" dimension, heft, and tolerances), and would you even consider that this "C" model might have better been named an "A" model of a different lineage??
An "apparently improved HP/IPstructure" Have you some idea what that would entail?? Thicker web, enhanced diaphragm dimension, and additional structure. That means a re-design, and an abandonment of the certificate. That puts the 900 effectively out of production. Over, Finito. The DEP method of sequential thrust enhancement is at risk.