Haha, the Number Bar as I mentioned can easily be assigned by the End User themselves without a Speed Book at all. Remember, assigning Keybinds is something you can easily do ingame, you could just rightclick a Spell and hit “Assign to Input” on the Context Menu, so you can assign it to 1, 2, 3, 4, 5, T, G, B, F9 or whatever you wish it to be, much faster.
What i do need to find a Solution for is scrolling through a Hotbar alike thing, though I can always just let the User themselves add or remove Hotbars at will, while also letting them specify the Forward/Backward/Select bindings for said Hotbars (and the direct Quick Slots for 1234567890).
The Mod you gave as an example is essentially useless due to the Game itself being much easier to use than a Book.
And in case of Wizard Spells, if you attempt using such a Spell the Player Animation could automatically grab the Book out of their Bag, hold the Book and start the Spells Idle/Casting Animation.