This idea has probably been thrown out there many times but I don't seem to find any of them.
I didn't look very hard 
Basically a Advanced Personal Chest can be shared by up to 5 people.
To allow someone to access the chest you wrench the top to open a GUI which lists the players already allowed for this chest.
You can select a empty slot to allow the next person to touch the chest to be added.
Anyone in the list can remove other players and anyone in the list can wrench the chest.
The chest doesn't add anything else new. Just the capacity to share it.
Anyone not in the list would see all the players allowed when attempting to open
Recipe for Advanced Personal Chest is a shapeless recipe
Code
Air : Air : Air
Air : Personal Safe : Air
Air : Advanced Machine : AirI wouldnt mind at all if this was made a mod instead.
Thanks