The faction play styles are actually based on the storyline and nothing else.
As you can see AC needs mobility and firepower to keep it's extremely spread out territories. So my logical choice was airforce for mobility and hvy ground forces to keep control. Armor Command is basically tank general on steroids while airforce makes uses of advanced drone technology and fucktons of air units.
WEA is basically at war with a far superior in numbers faction for decades. Add to that the fact they try to keep immigration as low as possible for financial/social reasons and their only choice was to go heavy on defenses. Europe is already in RL in a population downfall so by the mod's timeline open warfare with russia/china/india is not really an option for them. They had to entrench and prepare for urban/trench warfare - which means giving infantry a superior role. Continetal defense is basically close to usa's alexander being rather limited in terms of direct assault. It's basicly a turtler's dream faction. Mechanized assault while still having a strong defense, can also go for a more offensive style. Their unique vehicles however are weak on their own but when combined with infantry they become really strong.
ADF is a combo between russian tech and chinese numbers but also having a bit of a turtle in them. Ballistics command for example is a combo of turtling and fire support - in a way you could say they have a few things in common with ECA. Infantry on the other hand is the spam lord of this mod. They have weak vehicles that basically complement infantry and a huge variety of infantry. But their strength is epic numbers.
WLF - i will reserve details for later on them. All i can say is that lore wise they are no longer religious fanatics, but more or less desperate people who want to survive. Think of them as the Forgotten in the tiberium universe.
Well here is a bit of gameplay stuff. We are going to use a 3 level tier system. Each tier will have it's own units and defenses.
Tier 1 defenses counter tier 1 units in general.
Tier 2 defenses counter both tier 1 and 2 units but get craked by tier 2 artillery.
Tier 3 defenses counter T1 and T2 units and arty as well as T3 units but get cracked by T3 arty.
We will have at tier 3 a special building, unique to each faction, that gives a certain bonus - think of the RA2 ore purifier, industrial plant etc.
Airfield are gone for all factions. We are going for a RA3 style air combat so that dogfights would be possible. Basically all air units are either vtol's or helicopters/gunships. The only fixed wing planes will be for special powers ( Act of War style ).
Oh and most important - all factions will have the useless WALLS
.
This are some of the major changes. There are others but i can't tell everything
.
As for doctrines. All factions are both good and evil. To put it in short.
WEA - they went a bit nazi after ZH and the deep impact event. They ejected all muslims in europe after ZH for fear of any other events like that, they have a military rule made out of a federal council. And they don't give a damn if they have to kill half the world as long as the citizens of the alliance live well. They are also the only ones left with an active space program so that makes them the superior tech race in the game.
AC - look at modern day USA. That basically explains everything. Only in this mod they are alot more expansionist. This time however they lost most of their space tech as well as their space program. This makes them highly volatile (not knowing all the stuff they used to) and a bit paranoid.
ADF - think of russia's epic pride with china's epic iron fist and all of asia's huge population to keep under control. They are by nature more totalitarian, but also by situation. Having to control more than 4 billion people is frekin hard. And they still feel screwed by europeans and americans for not having the solar furnace tech. So there's also a grudge in their case.
WLF - this guys are basicly the good guys gone bad out of desperation. They represent eastern europe, the arab peninsula and what's left of africa. Basically the territories every other force is fucking with. All they want is freedom. order and respect. Sadly the only thing they get is hunger, diseases, corruption and lots of lots of dead. One can imagine how this situation would transform people. 99% of WLF members have seen family members die either to hunger/disease caused by political problems or killed in WEA/AC/ADF clashes.
I hope this explains stuff a bit.