[Imp]

In my view don't bother with the command units, they serve no purpose as cant be used in the command/rally chain.
Alternatively buy one or two & assign the odd unit to them.

If you ignore them keeps the unit balance ratio about right in most cases, as in tanks, infantry, arty.

So as an example of balanced force buy say
3 Tank Co
3 Infantry Co
1 Infantry Support Co
Arty assets

Now look at what space you have left & if you need further command units.
Possibly add a rear area Command unit for arty & AA
If you add say a tank command unit look at what to assign to him, most likely as hes thumb twiddling I would add SPAA as they will be likely to accompany the tanks. Or any other anti armour units like SPATGM, scout vehicles that you have.

Sort of off topic but relevant especially if a large force size, when it comes to buying units though I have a specific order I do like to buy in

1 FOOs
2 Most infantry units & there transport
3 Anti tank none missile stuff as in tanks ATGs etc
4 ATGMs & scout units (if possible & not included in the company)
5 AAA assets
6 Arty

Buying this way means the following
FOOs are easy to find
Less micro management as reaction fire order is
Infantry & transport
Tanks ATGs etc
ATGMs & scouts
AAA
Arty

So
Tanks don't get distracted so much firing at infantry
Limited ammo ATGMs only fire if need to as do scouts.
Your AAA & arty are last resort, hopefully you had someone to protect them if they need to fire.

If possible I buy MANPADS separately directly before my other AAA assets. Makes cycling through them easy if pesky helos are around.

I am happy to give up marginally better command & control options to buy my MANPADS & ATGMS separately especially in a campaign. Makes finding them easy & setting op fire filter a fast job as ATGMs are the one unit I tend to always use it on.