Thanks for the posts so far. I'm getting a better idea of the setting and the plot. I was thinking that Max gets caught up (as he often does) between a group of former MFP officers and the first of the crazies to come out of the cities and break out into the Wasteland.
The MFP officers could possibly be the precursors to the Gayboy Berserkers in RW, but for now they'd still be trying to help out the innocent and defenseless as they were trained to, although obviously with the country now a lawless war-zone they're fighting a losing battle and with limited resources, it's a struggle just to survive.
I've been thinking of a lot about the antagonists. I really want them to bridge the gap between Toecutter's crew and The Humungus' Vermin, both in terms of appearance and attitude. The Acolytes in the first film are really little more than a group of bandits who kill and pillage because they can, while Humungus' men are more like a small army, with rankings and caste systems. I'd aim to balance between that, with the chief antagonist being a man of vision going by the alias of Marko the Axe, who sees the Wasteland as a new frontier that he can plunder and take for himself. The rest of his crew would be made up of the mentally unstable, the dispossessed and the hedonistic trash of the Old World, who'd be the first to start looting and the first to take themselves out into the wilderness.
I'm still thinking on the potential appearance of the characters, particularly the antagonists. Obviously Max would be dressed similarly to how he is in RW, the former MFP would be geared up like Goose was in MM with the makeshift gauntlets and shinguards, but with the antagonists, there's plenty you could do with them. In MM, only the Toecutter resembles what would come in RW, with his furred epaulettes, eye makeup and snake-tongue helmet. Come RW, you have people in kangaroo pelts, shoulder pads, military fatigues and lots and lots of leather, amongst many other things. I've got some ideas, such as Snakebite's right-hand man (the 'Wez' of the story) being dressed in little more than torn up shorts and a bandolier, but nothing's set in stone.
As for the vehicles, they'll mostly be what you'd expect. Max would have a significantly grimier Interceptor, the former MFP would be using the old yellow, blue and red models (although some of them would be on bikes) while the villains would have a suitably diverse set of wheels. A few bikes, some dune buggies, a couple of modified muscle cars and an imposing, heavily armoured pick-up truck as The Axe's personal ride.
Let me know what you think. I'm putting together a little preamble for it.