Today I made it possible to use setups in GCM, where you place the objectives and starting locations and when you play with it, you can set one side to have less troops.
It's not really intuitive how to do it yet, and it's not all finished, if you figure it out that's great. To play normal battles, just leave the scenario set to "Customize".
The most confusing part is the "bid". When you create a scenario game, you enter a bid for both sides. Whichever side has a lower bid gets to be "team 1" on the setup. They also bring their bid's percentage of their troops to battle, while the other side brings 100%.
So say US bid 70 and CS bid 80, then US would be team 1 and have 70% strength, while CS would have 100% strength.
To make a scenario you use the options at the bottom of the SOW menu in the Launcher.