The sides are going to be Imperium and Revolution.
An Imperial Guard combined arms company supported by a Whirlwhind battery crushes Rebel Army forces in a ruined city.
Forces:
Imperium:
-Imperial Guard
Imperial Guard is in style of the one from Compendium. Highly mobile high-tech force. Equipped similarly to Space Marines. Tanks with force fields, heavy weapons with suspensors, etc.
Generally, it's a force worth shipping between stars instead of the current silly heavily armoured cannon fodder.
-Legio Juggernautica
Titans never existed. Instead of them, super-heavy tanks are treated like Titans. Equipped with void shields and powerful weapons. Baneblades replace Reavers, Leviathans replace Warlords.
-Space Marines
They have better armour and more unit types than in the original. Now their armour can sometimes stop a boltgun round.
-Loyalist Army
Remnants of loyal PDF. It's more similar to stereotypical Imperial Guard. They get the IG vehicles. Generally, their vehicles tend to be inferior, rely on autoweapons, have no power fields, etc.
Rebels:
-Rebel Guard (replaces Bad Moons)
Elite units of the Rebel Army.
-Rebel Army (replaces Goffs)
PDF.
-Rebel Militia (replaces Evil Sunz)
Militia is composed of armed citizens. They use adapted non-military vehicles. They get most of Ork vehicles, which I interpret as STC militarizations of civilian STC vehicles, not unlike RL Technicals, armoured trains and first armoured cars.
The idea is that most of STC vehicles can be adapted for use by militia by adding armour and weapons. They are worse than PDF vehicles but can get handy when fighting off a larger Ork incursion. Orks love them.