I like the look of that, Scaff. Do you think Kent would mind if we lifted his classification wholesale?

There are few problems for our purposes: older cars have worse tyres than the latest ones in GT4 (which was why I split them by age in the first place); the Caterham will be ranked with the likes of the Zonda, Ford GT and TVR Cerbera Speeed 12, none of which it can live with on a proper circuit; the Peugeot 205 T16 seems to have an unhealthy advantage against its peers; there's no classification for 4WD cars, although I suspect their performance would not be far removed from the FRs.
I would suggest a class system like this for each division. I think FF cars do need a separate class, as they will not be as quick as a FR, 4WD, MR or RR car with the same power and weight, although you're unlikely to get any FF cars except in the modern division. I doubt there is really any need to separate any drivetrain other than FF: I doubt that MR has an outrageous advantage over the others, but I may be wrong. Haven't finished my own work on this yet (it was interrupted by VTD 1). I think we may have to transfer certain cars between classes and divisions, so they do not have an unhealthy advantage or disadvantage.