The answer to your question may not be what you are expecting, it is actually technical limitation which is causing the Gree currency to be character bound. Within our current system we had a few options:
Those were our options from a tech standpoint and our justification for the decision we made. Hope that makes sense!
- The items are character bound and stackable (the way it works currently)
- The items are non-stackable and bound to Legacy. (we did not choose this option to avoid a cargo bay somewhere full of currency)
- The items are fully tradeable (these are meant to be earned, at least for now)
But what's keeping you from making these character bound tokens serve the sole purpose of being traded in bulk to a NPC in exchange for one unstackable, legacy bound token? Event rewards could then be purchased using 1-4 of these legacy tokens. Doubt people would think four item slots wouldn't be enough to be an inconvenience.
I don't participate much in the pve part of this event so things can remain like they are for all I care, but it seems like there are some clear workarounds that could be applied to get around these tech limitations (assuming that's the reason for the current implementation of the tokens).