What are the specs of the guitar in question?
Also, why a three way? Why not go the whole way and get a 5 way, so you can get neck hum, neck split, both (or both split), bridge split, bridge hum. Or even a three way with the usual neck both bridge, and a push pull/ push push, or even a regular mini switch to switch it over?
Many ways to go about it, and keep the regular switching system, so you're not sacrificing options