Nevermind, this is going to be a FCoreLib feature
Use NBT data to process the inventory, pros: does not lost any kind of data, books, display names, enchantments, everything will be restore like it was before, cons: the result string is not pretty and is not human readable :c Dosent metter how much I like the old system, this one is way better, and a lot of easier to maintain. Based on @Comphenix work.