Yeah good point. A fourth slot could be handled well, making it balanced and not too overpowered like
-orbs: pet tp bonus effect+50-150 each slot, pet movement speed+1-5%
-dims: occasionally spells cost no mp 1-3% or something
-tips: evasion skill+1-7/archery skill/mms/throwing
-slits: melee skill+1-15 weapon 1-7 on gear(just straight up new stat, that applied to any melee weapon and appears in the menu pushing up your blue box with a bit of acc/att)