Trump already learned how to go around the whole senate approval thing by appointing people “temporarily” without confirmation. He did it almost exclusively near the end of his term.
The constitutional issue is using the Act to appoint Cabinet positions, not lower-level department positions. This has not been tested in the courts. One "acting" appointment was overturned by a District Court Judge (Obama-appointed) when President Trump appointed Ken Cucinelli to a newly-created position, ruling that the position, being new, never had a subordinate in place who could be upgraded to "acting."
-PJ