Id suggest that maybe every 3-6 months give all those who have spent money on the CC market either a %10-%20 bonus to there CC,s
so if in 3 months i buy near on 20000 coins a free deposit of 2000 coins or so would be awsome. or maybe a unique unlock system of some kind purely about the style of your character depending on how many coins you buy in a 6-12 month period..
so if you buy 10000 coins you get such and such maybe leading all the way up to 100000 coins which would earn you a awsome prize but would have no affect to the way you play the game such as damage or pvp boosts but would just make you look awsome