Artifact Shops with Gozag
Give a small chance for each Call Merchant to use one of the slots as an artifact shop. Artifact Shops here refer to the unique shops that are only spawned by vaults currently: "{Foo}'s Quality Used Wands" "Zin's Purification Station" "{Foo}'s Pet Rocks" "{Foo}'s Snakeskin Shack" "{Foo}'s Off-brand Ammo"
This gives Gozag a chance to spawn stores with items that are literally impossible to find otherwise (Save a rare vault that is rarer than Gozag offering to spawn the shop).