What about putting speed differents in the game. Jazz the allrounder, Spaz agile but less armor/health etc. A new character could be a slow, tuf rabbit with awesome weapons and armor/health.

Or what about expanding the family? Eva and Jazz could have a little kid which is fast but has less health/armor and can't carry the larger weapons.

But plz don't put in another guy like Spaz. he has quite usefull skils, but his personality? Yack!