USF is short on MP in the beginning. In any normal build (3 Rifles into officer, but I think it is the same for 2 Rifles into officer), you will hit the 35 fuel for tech up way before you'd tech up anyway. The only way to make the teching up faster would be to reduce MP cost, but this would also mean that USF had a very cheap backup officer squad for the late game.
What I would have liked to see on USF is to make the officers into actual support units. The Lieutenant is almost a copy of a Riflemen squad, while the Captain has some quite limited utility. The major is good, especially after the sight buff, but with 3 models he can be easily forced to retreat. But the first two need something different. They could even get a single M1919 upgrade in my opinion to add more long range firepower for USF.
I have played almost every single RTS game starting with the original Command and Conquer. One of the things that Company of Heroes 1/2 does well compared to other RTS games is that you become emotionally invested in your Units due to the Veterancy system. In Starcraft if I lost a Protoss Zealot, Zergling or whatever unit it didn't really matter as it was just resources that I could easily replace.
I bring this up because the officers being "free" as part of your tech basically make these units the same as that Starcraft Zealot or Zergling. I don't really care if they die since they were free and they gain Vet much faster than Riflemen so losing them doesn't have that same emotional impact as it does when losing a Vet Rifle Squad does.
This is one of the things about USF that I dislike the most and would like to see changed. I agree with you that LT/Captain should be made into support units. They should be vital to USF and not just a Rifleman clone without a soul that you do not care about.
Losing "free" Officer Squads and having to pay for them would be a fair trade if it meant USF had easier access to HMG/AT Gun and making the LT/Captain have some useful abilities built in since you would be paying for them instead of getting them free.
While probably not broken, what would you replace the two commander slots with?
Assuming No New Abilities (Even though it would be easy to make new abilities)
Infantry Company
The M191A6 LMG Replaced with Advanced Infantry Equipment
(which gives Riflemen Flares and Rear Echelon Flamethrowers) Thematically it would work
Tactical Support Company
The M191A6 LMG Replaced with Rifleman Field Defenses
Same as above from a Thematic point it would make sense if you could drop mines/make sandbags as part of the "Support" or "Tactical" theme going on with the commander.
Both of these would fit these commanders well without changing too much.