I had an idea with enchantment books. Since it is possible to combine two books of the same value I was wondering if a feature could be implemented that does the opposite. For example, you could take a Headless 5 book and change it into two Headless 4 books. This would add more possibilities to enchanting. Then it would be possible to sell only part of an enchantment book. (Once I accidentally combined two books and couldn't revert it.)
