From: Denver Colorado
There is a method for activating Army Group B (and when you do this, Army Group South changes its name to Army Group B).
To do this, you need to take Rostov and the 3 cities across the Don River. I believe there is a limit on how early you can do this, though (I may be wrong).
Activating Army Group B is very useful because all Army HQs assigned to Army Group South become un-attached and return to OKH. This enables you to assign them between Army Groups for free.
A key element to better organizing is to assign the Romanian Army HQs into Army Group Antoniscu. This frees up space in Army Group South (but it costs about 80 Admin Points).
I also have a habit of putting 2nd Army HQ into Army Group North (for about 25 APs). This achieves a pretty equal balance, with Army Group South being over-limit most of the time.
Other things to remember:
Assign all SEC units to OKH.
Assign all Romanian divisions to Romanian commands.
I have a habit of assigning all of the Jager divisions to the Romanians (loading the divisions up with 3 SUs per division); they give a bit of staying power, while freeing up a few precious CPs. Note that this assumes you are transferring Romanian Army HQs to Army Group Antonescu.
Invariably I tend to need a German Corps HQ in the south as a sort of free-floating reinforcement. I usually assign this to OKH or to one of the RHG Security Army HQs.
All of this takes a LOT of Admin Points, though.
Since I play the AI, this isn't a big problem. Playing against a human, it probably would be.
Nonetheless, it may give you some insight into how to mitigate the HQ command limit problems.
Spring 2018-Playing: Demyansk Shield: Frozen Fortress; Advanced Squad Leader,
Rulebooks: ASL (always ASL), Holland'44, Demyansk Shield: Frozen Fortress