>The property keys used in a vertex-centric index must have an explicitly defined data type (i.e. not Object.class) which supports a native sort order.

I'm curious as to exactly what that means. As far as I can tell it just means "implements `Comparable`". If so, is there any reason to not have UUID implement `OrderPreservingSerializer`? 

If it's something that can/should be done, I'm happy to submit a PR for it.