Thanks for the citation. There's no language in that law that restricts the President's ability to directly appoint members to the military who are loyal to him. All it does is establishes a commission, chosen by the President, that can appoint members to the military. But it does not restrict the President from doing so. In fact the President is free to fire them all and let it languish.
Can you cite any other law or precedent that would restrict him from doing so?
The President is not capable of appointing members to the military unilaterally. Congress has sole power "To raise and support Armies" and "To provide and maintain a Navy." The President's role in accessions under title 10 exists only because Congress put it there.
There are 2 million people in the military. All the president would need to do is find a handful of existing personnel and organize them. He doesn't need to "raise" or "provide" anyone.
This is exactly how Trump organized the legislative coup within the White House. He went through the ranks of the DOJ to find someone who would draft a letter to send to all the states implying that fraud had been found (a lie) and DOJ was investigating (also a lie). No one at the DOJ would do this except for Jeffry Clark, a low ranking official who was promised the role of AG if he were to carry out Trump's scheme.
Can you cite any other law or precedent that would restrict him from doing so?