Glock 17 in 9MM, Glock 21 in .45ACP and Glock 22 in .40 S&W.
Gen 4 Glocks have a modular grip system.
The only confusion would be magazines in 9MM and .40 are nearly identical, so drop the .40 and issue 9MM +P ammo.
The only problem with the Glocks is that I’m sure the military will require some sort of manual safety.