Step 1) Launch two clients
Step 2) Join a game
Step 3) Have one repeatedly teamkill the other
Step 4) Buy a battlesuit/lucifer cannon with the one that just got 1000 free credits
Step 5) 
Step 6) profit.
Yes?
Except I'm not sure where you came up with that logic. Yetshi isn't changing the concept of Retribution-a payback in terms of credits that equals the amount that the player has
already spent on current armour/weapons/accessories-he's only proposing to change the conditions of when payback is due on the offending player so that the credits owed will be subtracted from 0 and go into negatives up to the limit (-9/-2000).
An idea I'm not a fan of. Knowing myself, one mis-aimed lucifier projectile could set me back the entire game. Perhaps a more sensible suggestion is to have the credits owed back over time. So, if I owe a player 300 credits (ohshitsorrymanIswearitwasanaccident) and I currently have 0, the credits will be payed back as I earn them until I pay them back completely (all in the same match, of course.)