GM did you set any weekly coins limit? If not, make it first question pool because we have coin system here, so it should be SET all from the start. You can't change it mid game because it's gonna be unfair towards players who worked hard from the begging. :)
EDIT: Please make one big question pool for coins alone because i see that we need unique, arena, gold coins for sos/som scrolls. Some of them shouldn't be tradeable but unique coins HAVE TO be tradeable because not every build has chance to kill unique. About arena coins - I'm not sure if they should be tradeable. I mean it would be nice but some people will find a way to cheat on CTF/Arena and farm these coins. Hope you will consider my suggestions. Have good day :)