I was watching Spartacus: Blood and Sand over the weekend. I think my leveling scheme for warriors maps well to life in the arena, with one exception. First, a brief design note.
The leveling scheme is the way it is because of its source. There are essentially three levels in Chainmail, Normal, Hero, and Superhero. There are more for Magic-Users, but for now we're talking about warriors. The other reason is that I never want players to lose that thrill of danger, the feeling that any given combat against an equal foe could mean death. So, I wanted to keep HD kind of low, and not let bonuses get out of hand. I want the player to have to accept the fact that there are some creatures out there that they can not simply outlast while they methodical bash their heads in. Sometimes it will take strategy, guile, and a willingness to fight dirty.
Having said all that, and based on Spartacus, I think there should be something between Sellsword and Hero. Not a full on level, just some sort of bonus. Something that says "I've faced death". In the show, while the gladiators first arrive at the ludus and begin training, it is mostly raw talent that separates them. Once they've been christened in the blood of the arena, they are different.
Anyway, I came up with the notion of a "Half-Level". At 6,000 XP the warrior can choose to take +1 Combat or +1 Damage Die. This bonus is part of the one he gets at 2nd level. So, if a warrior takes +1 damage die, when he achieves 2nd level, his damage dice will increase by +2, to a total of +3.
Additionally, at 6,000 XP the warrior receives 2 Quality points. Like the above bonus, these 2 points are part of the four he normally receives when gaining a new level. So, when the warrior reaches 12,000 XP and makes 2nd level, he will only receive the remaining 2 Quality points.
It's really just a thought. I'm interested to hear what anyone thinks.