OP, I think the one mistake forever should be adjusted too. Something like 1 every major patch cycle (x.0, x.2, x.4) would be enough without significantly increasing the GMs workload.

I would suggest regrouping the items for purchase to reduce the frequency of this error type. Right now, they are grouped by character slot (Head, chest, gloves, etc...) . I would just regroup them by role/jobs/main stat (Tank, Healer, Caster, STR/MNK/SAM, DEX/BRD/MCH).