Your cutting an awful lot of players out if you only count those with a minimum deposit.
I probably will always meet those requirements, but anyone having a good month without having to deposit will be unfairly excluded.
Perhaps giving coupons etc to Bronze VIP's and above would be fair on everyone. It would also give new players a realistic target to play for.
If withdrawals were subjected to a (one-off) deposit level (say $25-$50) there would be no issue with reload farmers.
Genuine Players would deposit (at least) this amount on their journey to Bronze VIP, opening up the remaining benefits, while reload farmers would probably never make the necessary deposits, nor would they make it to the Bronze VIP level.