My question is basically why I have to pay for the warriors mutation? More interested regarding the game balance. (for fluff I can imagine sacrifices, pilgrimages and other shits) To me mutations seems akin with skills (like special skill lists) which are free.
Another question touch the chaos centaur hired sword. As hired swords works for payment and expected to look out for themselves (like food, drinks, supplies, weapons) if they gain a mutation or choose one, they pay for the prize (from they payment) or the warband pays for it?