I would design US officer differently:
LT
a close combat unit armed with either sort range carbines or grease guns able to upgrade with Thompson with normal SMG profile (not elite Thompson).
Comes with Grenade/smoke grenade or incendiary grenade
Captain
mid range unit armed with carbines have access to grenades/on me/mortar barrage
Major
Support unit comes with super vision/FRP/and binocular able to have vision similar to SU-85
Actually your setup is not that different from what im trying to create.
According to my study, Usf Ofices officially have carbine as thier PDW so officer model, event major using carbine is very realistic.
About LT
LT carbine do have a close range profile so i think i will change all squad to carbine. My Lt do have access to grenade through tech and also have improve smoke laucher (longer range abd faster cd). I think having on me in Lt make sense since he is more oriented in offensive and leading the fight.
Cpt:
I also want to give him a carbine but end up with an invisible gun so i have to go back with the thompson. And im still working on him. I do think of give him off map but dont want it to overlap with major. What i will try is move ftp to him or some kind of suppression with the m1919.
Major:
As you can see, i already move supervises to him, and will try the rest of your ideas.