Ha ha!...a real can of the old proverbials!
imo the class structure is as fair as it can be, certainly in comparison with other championships.
I think that you'd be surprised that many of the quick cars are not just quick because they have loads more power. Typically, competent drivers will improve their times as they learn the car and the circuit. Also, until you are right on the limit you'll probably find that tyres and set-up can make as big a difference as an extra 30 bhp
I remember competing against a guy called Tony Hawkins who had a standard 1.6 K (unmodified) Superlight (138bhp). He was (is) a super driver and regularly put in times at most of the hillclimbs and sprints that I struggled to get any where near in my 180 bhp version!
So, short of having classes for every engine variant and wheel / tyre / suspension combination along with calculations for the actual power to weight ratio, it is impossible to be exactly the same and therefore guarantee that no one driver has an advantage.
The fact is that in motorsport there will always be someone who is prepared to spend more time and money than you in your class.
So, a thought!...Perhaps we could have THE Caterham Seven Championship and use one car?...it would keep the costs down...Pay £500 (80 drivers gives us £40K)...then we can all drive to the event in our own cars and thrash the @rse off of a shared car?!
Finally, from this jumble of thoughts, I agree with other comments - the biggest challenge is to beat your own times...else why would the really quick guys like Dave Kimberley still be motivated? And whether your fastest or slowest you always have yourself and some others immediately around you that you are competing with.
Cheers...Enjoy!!