Look for
ArmA : Combat Operations (Armed Assualt)
You can control up to 9-15 ai
This is for both singleplayer and multiplayer
You can tell them to mount things and attack specific things
My favorte squad command is the Formation
Go for "Formation Vee"!!!!!
Those tanks won't remeber what hitted em :P

EDIT:
You can control Motorcycles(Very hard to control lol)2 peeps, Trucks(Not very stong but you can make bases with them :P5 Versions(Base making and support (Repair, Ammo, Health?) Transport (Normal and Machine Gunner), Buses, Cars(It skins), Humvs(3 versions Normal,TOW(Misslelauncher), Machine Gun), Helicopters(3(4) versions Apache, Blackhawk, And those werid small ones(There are 2 one with ammos that are black and one with missles green), Planes (2 Versions A10 and Harrior)

EDIT 2: THE MAP IS FREAKING HUGE!!! it takes like 20-30 mins just to go around the whole entire map O.o