So essentially tweak warlocks spellstone and firestone, there allready is a mechanic that makes it last forever when u get gear set from npc character on blackrock and surprisingly it stays on when u enter new arena game, my idea is make it work indefinitely for manual application, or at the very least make it consistent on manual application without it dissapearing after u enter arena and refreshing its duration just like shamans weapon enchantments for example, similar idea for poisons if u want to go that far.

As far as balancing goes u can add some kind of special dialogue line to trainers that will make ur allready applied poisons / stone last indefinitely, i would not mind paying reasonable amount of gold for it for example 200-300g

Lock has allready a ton of preparation to do before arena starts and its kinda nice qol to have in my opinion, esp when its all ready implemented in to the core

Thanks