There is already the ability to register custom item resolvers for kits however there is no way to serialize items in a custom format

I would like to suggest the ability to register a custom item serializer that works similarly to the resolver

Essentially, add registerSerializer(Plugin, Serializer) (and unregister) where Serializer which takes in an ItemStack and returns a string and if null is returned by the serializer then Essentials default serialization kicks in.