[Kitsumi]

One interesting spin to this idea could be to use a seasonal tournament system with it. Roll the season every 60 days, and rank for a few different categories. The bonus given would last for the next 60 day season, and you could effectively rotate bonuses for different seasons.

Example categories to rank on:

Most Wars Won:
Rank #1.... Increase Damage, gang members now have "War Master" title on their name
Rank #2.... Increase Member HP, gang members now have "War Chief" title on their name

Most Wars Lost:
Rank #1.... Increase hideout HP by 10%, some title added to gang member
Rank #2.... Increase hideout repair rate by 2%

Most active members:
Rank #1.... Increase member refresh rates, title "Insomniac" added to names
Rank #2....


So you see, you could effectively use a system like this not only for gang wars, but to promote or demote any activity in the game accordingly.