Restricting strong boxes to bank only or putting a real slow/root effect on them is something that might have been appropriate at launch, but right now, it would be a huge annoyance to pretty much every single player to log in and find themselves slowed, encumbered, or outright rooted, or all their items stuck in overflow because boxes can no longer be used in inventories, etc. All these people would then be forced to immediately buy backpacks at pretty much any price in order to just get things back to normal again (and with that much demand, the prices would rapidly become astronomical as stocks sold out). None of these is an option that would make anybody happy about the changes and I don't feel they would be a good idea this late in the game.
The two possibilities that seem most worth considering, pending observation of how things go on Test server and feedback here, are:
- reduce backpack size so they're just 2 slots smaller than the equivalent strong box
- reduce weight of strong boxes
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