well Tycho you should have a read. Its a bit juvenile imho, but some of the 'scenes' described, and plotlines were not that bad. The author has obviously been reading too many 'Playbella' methinks ). The rest of the site is pretty cool, first time I have had a look.
How about Max stumbles upon the Halls of Justice (MFP HQ) and finds himself another interceptor. You can see in MM1 in the garage scene where Max see the Interceptor there are other MFP vehicles. I think there is one that has an almost rocket on wheels shape to it!!
This could be the way to bring the Interceptor back.
A sweet ride in the new movie would be a 2003 Dodge Ram 2500 HD or a New Viper powered RAM SRT-10 black with blacked out red bulb headlights, and big chromed 18 wheeler style pipes coming out of the bed, but not low, it must be slightly lifted(about 2-4 inches) with mud terrains and no tail gate. another awsome car would be a 2003 Ford Falcon FPV persuit XR8 ute...MMMMmmmmm.....sweeeeeettttt.
as long as 4 is nothing like 3 (i hated 3 with a passion) and has a lot of chases and wrecks involving motified, but not obsessedly modified (3) cars, it will kick ass!!
I reckon that in a deserrt setting, a falcon would (unfortunatly)be impractical. A volkswagen beetle (original) can easily run on prety much anything from 4star petrol to sugar based alcohol. So a dune buggy that runs on booze is probably likely.
Just had another thought: Maybe it all takes place on water. Max is a drifting mariner at this point and because of the global problems, the polar icecaps have melted and everyone dreams of finding dry land.....oh hang on, thats Waterworld. D'oh
I THINK THE MOVIE SHOULD FIND MAX COMING ACROSS AN AUSSIE CITY. THEN COMING ACROSS " RICERS"? BATTALING ALONG..WHEN HE COMES ACROSS AN AUSSIE FORD DEALER SHIP WHERE HE FINDS IN THE DEPTH OF RUBBLE A BIG ASS BLAST DOORS .....THATS OPENS TO A TUNNEL...WHERE HE FINDS A MINT FORD FALCON G.T. JOHN MOSS SPECIAL AND A WHOLE MECHANICS NEST ..PARTS WEPONS...AND A " BLOWER" ...."KICK ER' IN THE GUTS BARRY".....BLA BLA BLA....YA GET IT?
). The rest of the site is pretty cool, first time I have had a look. 
