I'm a bit confused on which part of the changes we can comment on here since the changelog topic that's linked has 2 sections and they are "Commander Changes" and "General Changes", the latter which is faction specific and the reason for the other topics I'm assuming?
Either way, I guess I'll just give my opinion on the Commander Changes section here.
For the British the Counter Battery being replaced by Hold the Line makes sense as it was nerfed into oblivion basically and not very useful however I think there were better alternatives to replace it with that would be better suited for more defensive and static oriented players like for example tank traps and so forth.
I am however very much questioning the mortar section of the Lend-Lease Regiment being replaced as that was the main draw of the commander, the main point on why me and several other people suggested it in the first place all those many months ago.
A lot of people will probably say that I'm biased because of that since I was one of the people that suggested and thus it's my "baby" that I will protect but in reality again as I said already my main idea behind it was giving the British a mobile-indirect fire that didn't cost fuel, thus a mortar team that could actually move.
I guess that's less needed now with the mortar pit being salvageable and less costly to field but still, maybe it could have been replaced by a 4.2 inch mortar using the Soviet HM-38 120mm mortar model or something, perhaps a Priest even?
For OKW again it's nice that the defensive abilities were put into a single one and for the Fatherland gives you something to spend your munitions on but I think something like hull down, a hidden feature of OKW tanks could have been put to good use here for those more static oriented and defensive focused people, similar to the British Advanced Emplacements, since that's the whole team of these doctrines.
The Artillery Flares being changed or replaced was indeed needed so that's a welcome change I guess, they were sadly very abusable.
Ostheer is in a bit of a weird position I would say.
The Commander Panzer IV could be changed up to be a more unique vehicle instead of just replaced like that without being either UP or OP in my opinion. Or hell, maybe it could even be turned into some sort of Ace unit or something with a command mode similar to the OKW Tiger.
As far as the Panzer IV J goes, I really like this tank but the only issue I have with it is that I think the name is wrong. If it's the Ausf J version then it would mean that it lacks a turret rotation motor thus making it cheaper to produce but since the turret is hand cranked it'd be slower to turn obviously as you can read here:
https://tanks-encyclopedia.com/panzerkampfwagen-iv-ausf-j/
So the more correct name would be Panzer IV Ausf. H since that's the version of the tank in the game I believe, fitted with the "Schürzen" Armored skirts and the final version of it's 75mm gun.
Festung Support has some interesting changes with the Supply Station which is our real first glimpse of it in real use in the actual game, altho losing it's Artillery support unit is a sort of downside of it as well perhaps.
German Mechanized with the new Vehicle Repair Crew ability might also peak the interest of other tank heavy users like me but to be honest without a tank call in I don't see it being used all that much even with that for just 1 new ability.
Joint Ops again might see some more use from static focused players.
I don't really have an opinion on the rest of the Ost changes since I don't really play those commanders. Sadly Mobile Defense lost it's appeal with the hard nerf to the Puma, maybe something like a King Tiger could bring it back up.
Speaking of which, it actually brings me to a suggestion on how to implement the KT in to the Ostheer as a doctrine unit. It could be modeled after Kurt Knispel who is still the top tank ace in the world with somewhere 168 "confirmed" tanks destroyed, altho some say it could be more like around 200 but anyway, the tank could be an Ace or a Commander variant of sorts with the unique ability of the S mine launcher, similar to the Sturmtiger, which would be completely new for the Ostheer, plus instead of the Panzer Tactician smoke, have Sherman like smoke ability and maybe even an infantry inspire ability? The possibilities are really endless.
I don't play Soviets so I won't comment on them and thus I end my somewhat long post here.