So finally got the chance to see Mad Max: Fury Road.
It rekindled an idea I had for a convoy system for the Realms of Darmonica setting (of which Frozen Skies is part of), though its always taken a backseat to Frozen Skies. Some of the adventures I envision taking place in the world of Darmonica I view as the players being part of an outfit with a vehicle, either an aircraft or some sort of ground vehicle. Both generally will have the same format with pilot/driver, mechanic and dedicated gunners/fighters for defence. There is the optional support staff like the moneyman, etc whilst ground based outfits lean more towards being convoys with dedicated scouts, navigators, possibly even a commander who's in charge and perhaps a radioman.
Now the mechanics for a convoy system are more likely to be included in a general Realms of Darmonica core book, Frozen Skies is really more of a region guide/supplement and has a different scope. Thats not to say that convoys won't work in Alyeska, after all aircraft can only carry so much and railways are rather thin on the ground. Convoys could also work wonders for expeditions, or a relief column as part of a military game set in the Wulflands for example.
The Mule works, though more vehicles are going to be required and I do envision 'rigs' which are effectively a road train. Each trailer of the rig (chiefly when travelling through dangerous areas) are likely to have what are basically turrets or gun positions, either a fixed machine gun or firing point for a rifleman. Again convoy rules and the extra vehicles are unlikely to be in Frozen Skies, though if you wish to do a convoy based game then use the Mule, trucks from Deadlands Noir and the Semi in the Savage Worlds Deluxe rulebook (though limit it to three trailers each with a single 'turret').