for cannibalization, you'd still have to understand how the keyboard matrix works. someone has done that before on geekhack, with nice results; but you'd still have to know how to wire things up so that whatever firmware you're going to use will take. look at leeku's split boards as an example
http://geekhack.org/index.php?topic=40880.0the easiest way to achieve a custom physical layout that resembles the wave shape of the NKP would require you to be able to make your own mounting plates for the switches, assuming you're using cherry mx switches, and wire those by hand. Making the plateswould require some cad work and a lasering shop unless you're able to mill your own plates.
From there on, the split design would is tricky - I would suggest looking at the ergodox's wiring, replicating that while arranging the positions of the switches handwiring those. that way, you could reuse the ergodox's firmware on it if you're not able to make your own firmware.
Keep in mind that replicating the 'wave' on the NKP would mean that you wouldn't have the wider keycaps of the NKP to fit on it; ie. there would be gaps between the keys, unless you're going to make your own keycaps.
For curiosity's sake, what is this 'wave' you're talking about? I'm assuming you're referring the way the NKP has the keys wider on the higher rows, and not how the two sides are angled, as the ergodox is able to be angled any way you please. Some clarification would help.
Alternatively, if your pockets runs deep enough, you could contact maltron for a custom job.
http://www.maltron.com/component/content/article/214-keyboard-information/465-bespoke-projectsI
believe this was a geekhacker too, and (probably mistaken) remember an approximate quote of about 800 bucks for the custom, but best to check maltron.
