I have heard many valid points in this thread that apply to the whole mix in racing. We may have strayed off the topic a little so please accept my apologies. In my thinking racing is all about the whole package. It is about the rider, the brand of bike and the assets it contains, and the amount of money I am willing to spend to overcome the liabilities/deficits. Put my whole package together against some other package and we have a race.
The small rider has an advantage over the larger. I can lose weight but not as much as cold when I was younger. So I add horsepower up to the limit of the rules. Hopefully the lighter rider doesn't have enough money to do the same. For me I race on a budget and choose not to spend as much as others, but I hold my own when it comes race time. eat I hear the saying, "if you can't afford racing then maybe you shouldn't be". I race with what I can afford.
Lightweight for me is a good starting point for any racer. It offers the new rider a chance to practice and hone skills without the threat of tremendous speed or power that overwhelms the rear tire traction. On the other end of the lightweight spectrum where all the fast experts ride can become very costly. But that's only if you choose to spend that much.
A new Rider in the larger class' already have more than enough power to overwhelm the rear tire and speed to overwhelm the senses of the rider. There is not as much need to upgrade for more power. There is a lot more potential in the ability of the rider before performance upgrades are necessary.
Now, tire choice. I use the tire of my choice because I want to. If it fits within my budget and provides the results that I need then it's my choice.
Rules are there because it helps to delineate the difference in the class structure.
