Currently the Panzer IV is in a very awkward and controversial position, it's too weak to be used in a combat role but it's bonuses provided to nearby both vehicle, infantry and allied units alike is a bit too good and promotes blobbing around it for a lot tougher snowball of death rolling through the map.
So what I suggest is something like the current Tiger Ace with it's Spearhead mode but even without it it will have a permanent lower accuracy and reload rate (due to all of the extra "radios" inside). Command Tiger also has an air recon ability similar to the British designated command vehicle. The command ability when activated acts the same as the Sherman radio net bonuses, ONLY FOR YOUR OWN VEHICLES/TANKS at the cost of more of the Command Tiger's combat capabilities because "the commander is too focused on leading the tank force and cannot concentrate on also leading his own crew at the same time".
Now what this will do, at least in my mind, is cut down on blobbing around the command tank (the Command Tiger in this case) and also "buff" the currently I would say, lacking, doctrines in which the current Command Panzer IV is in right now.
So here's the list of the 5 doctrines I have found the unit in:
German Mechanized doctrine -
Only problem here might be the Spotting scopes but I believe there was another commander with both the Tiger and Spotting scopes, not sure, so theoretically, it shouldn't be a problem also taking into account the tank's cut down combat capabilities.
Blitzkrieg doctrine -
There's Spearhead already with the Panzer Tactician smoke so it shouldn't be that big of a problem.
Mobile Defense -
This doctrine has fallen out of favor with the "nerfs" to both the Puma and Osttruppen reserves so I think it would be a welcomed change.
Festung Armor Doctrine -
A pretty mediocre commander even in the early days of the game back in 2013, uhhh I wouldn't say there's much to it besides the Panzer Tactician smoke, Railway Arty which relies heavily on RNG and the Command Panzer IV itself. Hulldown is pretty underwhelming as an ability right now and the Pak 43 just gets annihilated by offmaps for the most part, making it's investment largely questionable at best.
Panzer Tactician is already present in Blitzkrieg so hulldown I don't think would make the Command Tiger any more OP or anything, besides providing it with a bit more range perhaps.
Fortified Armor doctrine -
Now we come to the fun part, again there's Panzer Tactician and Hulldown but the Elefant as well, recon I'd rather have replaced with spotting scopes but that's just entirely my own (evil) dreams.
Historically speaking the 653rd Heavy Tank Destroyer battalion which is most famous for using the Ferdinand tank destroyer on the Eastern Front had the only Porsche Tiger that ever served as a command vehicle which was also fitted with an additional 100mm armor plate at the front, making it 200 in total.
So this would really be a nice reference to that but for the sake of balance perhaps only giving you the option of either calling in the Command Tiger or Elefant would be the proper thing to do here.
Now to end this long post a little TL;DR:
Command Panzer IV becomes gimped Tiger with commander ability that ONLY AFFECTS YOUR OWN VEHICLES similar to the Ace's spearhead mode and the command aura/bonus is similar to that of the radio net of the Shermans. Improves mediocre commanders in which the Command Panzer IV is already in.
Pic for reference -
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And yes I am aware that the picture is from a CoH mod and not from this game, I'm just using it as an example because of the maps and radio antenna on the turret altho the black skin is present on the workshop for this game and would be nice to see in the vanilla game.