Okay so first things first, I'm not saying this because I just got a map on ksf myself. I know most of you morons will say that anyway but maybe you wanna hear me out first.

After going through the whole process of getting a map on ksf (eventhough my map sucks ass and didn't nearly take as much time as most other maps) I realized that mappers are essentially people who put dozens of hours of work into free content for you to enjoy.
So my suggestion would be to reward mappers with vip for limited time, whether it's one set amount like 1 month or separated in tiers depending of how much effort is put into the map and how much content it provides.