I dont think so. The same issue of the need for senate confirmation will result in the same conclusion because the judicially determined classification as an inferior officer remains the same. Whether appointed by law or regulation (which by the way has the same force as law) the fact that the official is inferior is what determines if senate confirmation is required. Or so that is what the Supreme Court has ruled. Stare decisis makes this determination irreversible case law on this isuue. Your argument that genesis of the appointing power is determinative was not what the court ruled was correct. And since the USSC decides what the Constitution requires I would suggest that their interpretation is the correct view of the law in this instance, and not yours. Just saying.
You can’t take a court decision interpreting the language of a statute that provided for independent prosecutors and claim that it controls the interpretation of completely different language adopted by the DOJ in its own regulation creating a different government official entirely.
“the Special Counsel shall exercise, within the scope of his or her jurisdiction, the full power and independent authority to exercise all investigative and prosecutorial functions of any United States Attorney”
Here, by this language, the DOJ has unilaterally attempted to create a de facto US Attorney.
Yet 28 U.S.C.§ 541 adopted by Congress requires US Attorneys to be appointed by the president and confirmed by the senate.
This question simply wasn’t present in Morrison v. Olson because there was no question there that congress had authorized the legal office in question by statute.
The question here is entirely different, has the DOJ gone beyond what it can do by unilaterally creating a de facto US Attorney, which Congress did not give it the power to do?