Maybe when you're in WoE and the really super-hardcore with ah extra violence Many Players vs Many Players starts you click everywhere like a :genius: person and accidentally click the cash shop 0: on super extra mega intense pvp xD so you know what happens next
I don't think it'd be such a bad idea. There could be places where you dont want the Cashshop to be opened and vice-versa. It's not that bad of a something to add in.
This is a nice idea, my players are requesting this too since it becomes annoying when they accidentally clicked the Cash Shop button while in PvP and WoE.