just make the free content to serve as some kind of a demo. a few ffa servers with a few maps like dm7, dm17, t1,t2 and thats it...

it will be full of cheaters but who cares... just make people know when they sign up cheaters go away and what only remains is fun, fun, fun...

than sell the following packages:

10$ - unlocks CA, TDM, FT, CTF , duel, and all non-competition maps.
this what u can call the "beginner" pack, would make sure servers are stay low-skilled as a skilled person probably not want to duel on eviscareted / nameless place etc for eternity... or neither buy this package at the first place. also this would get rid of the blatant obvious cheaters. those who manage to sneak their way in would probably stay unnoticed by noobs anyway.

25$ - all mods + competition maps. if you want to duel on ztn cough up that 25$/year.

50$ - server spawning etc...

here you go id, figured out for you for free