A fairly simple concept - have a locker that all cabal members can access. Perhaps with a capacity of 100, 200 items (whatever works).
We could argue all day about whether or not it would be able to contain a (limited) number of rares, at a CP cost to the cabal. But it would be cool for more experienced cabal members to be able to fill it with mundane re-equip suits, useful items, consumables, etc. for newer cabal members.
Yes, WoW players. Guild banks.
Can't you do this already with the treasury of the cabal?
There's already access to mundane re-equip at the cost of 50 CP (outfit).
The treasury as I understand it is little used except for votes and erecting bastions for most cabals as the buying of rooms hasn't been around since 2.0 (to my knowledge) and the tithe system is fairly defunct for want of cabal politics.
By the way, the cabal map command does some funky stuff.
Mundane re-equips can be done with cabal outfits.
Merchant cabal helps in this regard, too.
If it's used for rare storage, it's going to be abused. Imagine Warmaster hording full adeptus suits to prevent anyone else getting them. Removing lamian staves and wands of wind and rings of accuracy completely from circulation by Cabal A.
Currently, it would boil down to an interchangeable consumable-and-cabal-equpiment storage.
Already have a locker system. Why double down if it's not going to have rares. Rares shouldn't be stored in lockers because of hording which people already complain about.