If your internals can't work with theirs (I would doubt that they can't work together), then it would be ok as it's own module. It just seems that this would fit nicely, at least into IxHash. It keeps the order of the entered keys, but also has some ordering/sorting methods (Reorder, SortByKey and SortByValue). With add something like SortByInput (off the top of my head) it seems you would only need to reorder the array IxHash keeps in parallel to the hash.
Just my $.02, but I do like the idea. I would only want to make sure it wouldn't be more valuable in conjunction with another module, rather than stand alone. I suggest asking for any comments on the modules list.

Cheers,
KM