I'm against permanent stats boosts in any form (switching cheap stat for expensive stat included) or any additional advantage as reward. I dislike the blood games achievements like +833 block +667 bleeding and + 667 armor and I suggest to actually remove them unless you can argue why 15 times winner would need such enchantments.
I like:
- vanity gear;
- special text lines at the beginning of arena match / during fight / on winning the fight / using abilities;
- gladiator name in the rankings can have different color;
- things that won't influence game balance;