One way would be to let the characters choose their roles - squad leader runs overall tactics, and let the other players take on specialty roles - EOD, JTAC, medic, etc. A sniper could lead a few NPCs as part of their team (spotter, security, etc). For this scenario, with the players mostly mounted, each vehicle could be led by a player.
We did have one group play in which the GM role-played the soldiers based on the situation.
On Reddit, we dropped a spoiler from the Core book that covers a very similar scenario where four characters play: 1 as the squad leader (lead vic), 1 as the sniper lead, 1 as a medic, and 1 as a JTAC. In any case, let us know how it goes! If you do not want to click on the link, just search outsidethewire on reddit.