I knew I'd seen it somewhere...
This Thread, (by all accounts) contains a mission which should allow you to control a platoon of AI soldiers in a MP/Coop environment. I haven't tested this at the time of this post but will do later tonight and will report back with any new worthy info.
From the thread...
# Mission Features
* Control the behaviour, combat mode and formation of each squad.
* Make Platoon formations as described here.
* Order the men to mount/dismount their assigned stryker.
* Order them to move via map clicking.
* Order them to flank in an intelligent way (i.e. they won't cross your line of fire).
* Watch a bearing.
* Advance in a certain direction
* Adjust the spacing between the squads
* use the minimap...
* Adjust the background colour of the dialogue.
# The mission
They put you in the shoes of a Platoon Leader, but you can play along with your mates, as the 42 slots left are all playable.
They come with a full briefing -which also contains the manual of the dialogue-, custom sounds and surprises.
They are basically for committed players with an interest for missions with a tactical edge. Don't expect to slaughter a company all by yourself here.
# Known issues
Although the net coding has been streamlined, the Strykers sometimes just won't move on dedi servers, especially in cities. I haven't been able to carry out comprehensive testing on dedi servers yet as I don't have any handy.