There is no way to level the field and no reason to do that. If a guy wants a better car within the rules then so be it. I have not heard of any cars that do not fit within the rules.
There is no way a new driver with a slow car should be as fast as a seasoned driver with a great car. That is a recipe for disaster. There will be lots of contact due to lack of skill and racing technique.
I am certain that the guys at the top of the heap have many years experience and put in the time to get there. I know my personal journey has been 15 great years. About half of that has been in entry level spec classes. It is the best way to go racing IMO.
There will always be tinkerers and guys who like their cars to be the best possible inside of the rules. There will also be the guys who are satisfied being mid pack and get everything they need and want in that position. All drivers should earn their finishing position based on skill and car preperation. Financial ability will always be a factor in racing. Some guys can afford to have their stuff professionally prepared others take pride in doing it themselves. Some can afford to always have premium tires others are just getting by from race to race. Just the facts of life. We all have to deal with it.
If the data proves that there needs to be a competition adjsutment then a power to weight ratio would be the best way to do that.
The fine points of where to put the weight and how to administrat it should be another discussion when we get to that point.