1. Probably not, the main thing I would use the transfer book for is to move all the items to my character with barter for selling. Pretty rare I sell food or scrolls.
And what about all the recipe books to get rid of?
2. If it doesn't cause a problem, I don't see why not. But if it does (or more work than is worth it) then don't worry about it.
I better restrict starting transfer dialogs via backpack to a small amount of characters as long as I don't see a way to tell Osiris which non-global backpack a character started a dialog with. Only the char script knows, but it can't tell, Osiris doesn't listen!
Osiris can pick up a CharacterItemHandleEvent() for non globals, so even non globals can communicate.
That's what mines do after all, they communicate back and forth with Osiris. (GLO_Minespot.itemScript and LUC_MineBlackRock.txt)
You only need to find the 'event actors' for the event, which you can ignore in Osiris as desired.
I'm not sure if a dialog start throws a use event though, but dialogs can set their own events and they have their actors ...
3. I never use containers really so I'm a bad person to ask. Just creates extra clicking.
For the same reasons as 2. I better make restrictions here if it's not highly desired.
I've added a book with information about all contained items and functions now, added a Me to transfer dialogs and fixed a potential problem with crafting in Coop.
I'll upload the update tomorrow.
