First yes the storehouse does exist
- if you do not have a build going and collect surplus resources you will notice after your build tick there are resources in your citadel already.
So when I read your first post what I thought you meant was if there was a surplus in the citadel lets say 1k which isn't going towards a build then it can in essence be claimed by people so they can do 1k less resources so their resource cap at tier 7 would be 1k/2700.
I'd support that idea but it gets messy as it will get to the point someone can just enter citadel and becuase there is over 2700 resouces surplus they have basiclly capped and can claim the clan fealty and bonus xp.
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The idea of trading it to players and being able to continue is a no - Both Mod Maz and Mod Matthe have said No to this - At the end of the day it can be sold as others have said, and the xp rates in the citadel aren't bad so people people could just get 99 smithing/crafting/cooking for free with no need of banking and very little effort (minus crafting plot)
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Turning them into actual resources is a very BIG NO
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An idea which was pitched before was to give players an option - they can cap as normal
or
Select an option which will give a diminished amount of xp but you will cap really quickly