The only problem with proper class refinement is that to do it right, you need a lot more participants, otherwise everyone gets 1st place. And also there is a lot more work in scrutineering, otherwise everyone can sandbag their car to 150hp. For instance, in CASC, they want dyno plots so that a car with an engine swap netting 20hp (like an M50 E30) will not be in the same class as a stock GT2 (530).
The CASC car classification site is free and it has just about every conceivable car. Then you go through a simple series of questions asking you what mods you have, and it spits out the class for you. So maybe next year, time trial entries would be required to present their CASC classification results (and then have common sense applied to whether or not it's sandbagged), then perhaps group cars together that are close enough, to not have too many classes. So like if you have 5 cars, 1 Prepared, 2 Modified, 3 SGT1, then maybe put them all in Mod... etc.