The SCI interpreter doesn't exactly have "adventure game" capabilities built in. 95% of the game is the class system (scripts). All the SCI engine does is provide a virtual CPU, graphic, sound, windowing, input and list management. All of the rest of the stuff, eg. ego, dialog boxes, what keys are hit, the inventory, displaying the inventory, actors, rooms, etc. are all in the scripts.
That being said, since the interpreter doesn't actually handle inventory, the scripts do, the current inventory system could be classified as "custom". That being the case, you could easily modify it to your liking provided you have the ability to code scripts.
Almost anything you desire for your game can be done by modifying the class system scripts.