Acceptable, it does seem like there would be some incentive to award a top performing faction weekly/monthly. Seems like that would drive up player investment if you knew it determined things your faction would receive. But at the same time you don't want to alienate factions completely. There will likely be many groups of friends who select different factions for various reasons and you still would want them to play together. For all we know the factions may be skill based and it benefits you to work with other factions members.