This is a common idea, but the concept behind it would say that if you're good, you get better. The problem with this is obvious, it spaces the leetness gaps even more, say I am a Tyrant, go around and totaly pwn everything, I get more powerful, eventually I could be near unstopable. We would need some sort of handi-cap system to balance this.
Neutral: let's say you are a Tyrant, and totally own everything. What Rewards could you get?
Remember, you can only have one Reward at a time.
What classes of activities would you be involved in?
You would probably
Hunt, and
Destroy (although on some servers you could also
Heal, but maybe makers could make it so you had to
consciously heal teammates
or possibly be denied the Rewards if you had engaged in a lot of teammate-damage-dealing - e.g. no enemy present + full health+ damage any one teammate for more than 50% health).
For hunting you would be handicapped for killing enemies beneath your stage. The best reward you could be awarded would be Stealth, for killing a same-stage enemy. You can't get Cloak, and you can't get Invisibility, because there are no enemies who are a higher stage than a Tyrant. And if you didn't refrain from killing lower stage enemies, you could possibly be given either Toxic or Hazard (and would be dangerous to nearby teammates or your own team's buildings).
If you were out destroying enemy structures, you could get Strength, Speed, Endurance or Regen, true. Very good Rewards. But the idea of the mod is to drive the type of play that Tremulous players always say they want. That is, players attacking structures, with kills as collateral damage, and inevitably as the way to stage up (but you could tweak that, too, by making stage-up dependent on destroying, building and fixing as well as hunting).
In the rare case that you were a Tyrant who was actually engaged in healing teammates, you might possibly be awarded Reflect. Which would make you want to heal teammates, instead of randomly slashing at them, as you charge away from the enemy base.
Also, one thing that is yet TBD is how many of each actions you would have to perform to get awarded the Reward, and it could possibly be stage-dependent (harder for rich humans, big aliens; easier for poor humans, little aliens).
Note, also, that the coolest Rewards are for damaging structures, or killing enemies who are stage-up from you, which aren't even really acknowledged by the current scoring system. You also get fairly decent Rewards for building and maintaining successful structures, another item that never shows in the killcounts (although it directly affects who wins). Healing teammates will become an action players will find worth doing. And the "bad" stuff - killwhoring, TKing, and damage-deconning - will get you a little in-game detriment (which can be used creatively).
Build - Destroy - Hunt - Fix (Repair/Heal)
Plus, as Ris has suggested, if you get one of the Rewards, you could get a Q3a-type badge over your avatar's head, and the in-game voice says the name of the Reward -
"Vengeance" - in that robotic god-voice from the Arena.
Alien-Vengeance Mara+, FTW!!!