Time for an update: I've tweaked the key item usage code to delete 8 useless key items from your inventory after their last known use. I suppose I ought to dig deeper and go through the data for what key terms and items a given NPC has text for, not just the code for doing non-text stuff; work, work, work
. The new code seems okay in the few spots I've tested, but it'll probably require a complete playthrough for full confidence. I've roughed out a bunch of NPC and event flag stuff, mostly in bank E; if we ever need large amounts of space in banks 3 or E, those banks each have a pair of 256-byte lookup tables (for a total of 1024 bytes) to map 8-bit bit indexes to the corresponding byte and bit (e.g. to map flag #$5A to bit 1 of byte #$0B) that could be replaced by about 20 bytes of code (which might already exist somewhere!).
The Mythril and Wyvern Egg were already removed once you were done with them; now the Pass, Goddess's Bell, Egil's Torch, Sunfire, Pendant, White Mask, Black Mask, and Crystal Rod are also removed, leaving you with only the Ring, Canoe, Snowcraft, and Wyvern summon. If you decide to fight your way into the Dreadnought, the Pass now gets removed from your inventory and the chest containing the pass gets marked as open (whether you actually opened it to not) in order to prevent picking up the Pass after the window for getting it out of your inventory closes. The Wyvern summon is a potentially useful battle item (and you can decide to have Ricard take it with him when he goes), so it can stay, but for the others, the game only checks the list of obtained key items to determine whether their abilities apply on the world map, so if we wanted to we could basically convert the Canoe and Snowcraft to non-inventory items. The Ring could be removed from your inventory after you show it to Hilda, but that would be at odds with her dialogue where she explicitly tells you to keep it; I'm tempted to suggest some light script revision there, either to have Hilda take the Ring or maybe just have one of the characters wear it. I found myself having to throw out useful items quite often during the mid-to-end game, so freeing up 11 of your 32 inventory spaces would be pretty awesome. However, I'm not sure whether this should be considered a bugfix or an improvement.
In other news, how would you feel about re-ordering the naming screens to match the character order, i.e. Firion/Maria/Guy/Leon instead of Firion/Leon/Maria/Guy?