*Sigh* take another idea:

Ok, here's another idea, yadda yadda yadda THE ITEM UPGRADER. I'm making some speculations here based on the general shape of the blacked out spaces in this merchant.
Teleportation Scrolls: One of the places is in the shape of a teleportation scroll, so I propose that teleportation scrolls be able to be combined or upgraded to get multiple locations on one scroll.
Potions: One of them is in the shape of a potion, so I think we should be able to upgrade all of our potions instantly to the max level we currently have available in a snap, saving money.
Emerald Pouch Image: Upgrade your emerald pouches to higher tiers without needing to buy a new one.
Ingredient Pouch: The bigger of the two pouch slots, you can upgrade the number of slots in your ingredient pouch.

 

My assumption for Emerald pouch/pots is more or less the same and would be hella fire GIVE ME BETTER PUCH
Not sure if ingredient puch one is possible? given MC container sizes...
TP Scrolls aren't really a problem: with 3-4 you can do a lot and even then 1-2 are conveniant and rarely used.