I can see where you’re coming from on this, but I quite like the Verteran levels. They’re a small bonus, but you don’t feel you’re wasting XP by keeping your Veterans in the line-up while you train up new Battle Brothers. It keeps the Veterans getting something while still keeping them in range of your lower level brothers and the enemies.
I worry balance would be sent of out whack by larger gains/specicial perks etc.
Current system seems in the sweet spot to me.