A new look at a fair RB?

Why not? Yes, let the weak and skinny begin, and gradually they will build up fat and muscle. With a lag, send the next and next. Let the curve of difficulty increase gradually.

add
(Simple amateur solutions)
Set Pandor Balance for Veteran. Reduce the number of Pandors on first appearance for beginners. Then everything depends on how to set up the evolution system + dynamic difficulty.
Adjust the balance of skills for Legend. Increase bonuses and decrease the cost of skills more and more for each difficulty down: Hero, Veteran, Beginner.