Some[list] (pointless) suggestions for the next AC Toolkit, as well I've taken the liberty to figure out a (near exact) location in the save for some of them:
Editing Redd's items.
Editing GracieGrace's items ($6319C to $631FC), including the 'preview' in the top right ($7361A).
Editing HRA items ($636E8 to $63B44 [and/or] $641F0 to $64644).
Editing town tune ($7359E to $735AE), including normally not selectable values ($20-$FF)
Editing/Adding/Deleting letters in your inventory/storage/mailbox, as well as converting them from 'received' to 'sendable' letters and vice versa.
Editing/Adding/Deleting message board posts.
Replace (item) with (item) ability for the world map.
Museum editing (What it has, etc)
Editing fish/bugs caught for players.
Editing wallpaper/carpet/music playing for houses, as well as a 'cockroach detector', and editing the 'save' floor's bed.
'Replenish fruit' button for trees on the world map.

I realize it's a lot and that most, if not all won't be done, just figured I'd point out stuff that -could- be done.