I feel what was done with spells was a very good thing - in the click, and choose the level.
I would actually suggest hiding all the spells into ONE menu- a spell book on the hot bar- making it similar to the how it works for choosing the level of the spell.
Click the spell book, and it has tabs, 0 through 9.
Click the 1, it shows all the level 1 spells, and only the level 1 spells that are memorized and usable.
Click the 2, shows all the level 2 spells, or spells that take level 2 slots.
etc etc.
Choose the one you want, click, target, click, move on.
