He also needs to cut the Pentagon staff by 25%. Send them out to line units, and if there aren't enough slots, the Reserves and National Guard could use a bunch of full time help.
I couldn't find current numbers but here's from 2016:
As of Feb. 29, 2016, there were 411 one stars, 299 two stars, 139 three stars, and 37 four-star active generals and admirals, with several more appointed recently
That's 886 for 1,281,000 troops (enlisted and lower ranking officers). Seems top heavy to me.
In 1945 there were roughly 1889 flag officers for 12,056,000 troops (enlisted and lower ranking officers)
We had 1017 flag officers at the end of the Cold War. That's only 131 less then what we have now and we had 2,130,000 troops on active duty. We've cut 900,000 troops since 1989 and only 131 Flag ranks.
No wonder officers spend a lot of time doing NCO Business...