no just no please.
if a piece was stored with WAR job slip, will you allow that piece be withdrawn with SAM job slip? If you can, then why not just proposed to just combined all slips into 1 single slip. If you can't, then imagine the headache one would have to keep track of EACH piece as to what job slip it was stored with.
the better solution is to get rid of slips altogether and rather just turn them all into KI(s) if absolutely must. when you talk to the npc, it'll ask you which slip ki you want to access and you select the one you want (using the current system breakdown is fine).