Civil Service rules passed by Congress virtually makes what you suggest impossible. Built in rules like if you change the job classification of a Federal Employee to a lower pay grade, they still get the same salary for 3 years, so it does nothing to cut pay. Then there are the appeal rights whenever pay is reduced. This isn’t based on Union contracts, this is Civil Service Law.
I'm sure none of them are aware that my having fought a legal battle to win two major precedents in civil service administrative practices was, in effect, a multi-billion dollar accomplishment.
The real solution would be to repeal much of the civil service law, and bar unionization of federal workers.