Swapping lens mounts is entirely doable. I have several such modified cameras myself. For example, Panasonic (GF1, GH2) with M42 thread mount instead of the bayonet, likewise Sony NEX3 also with M42. The reason for swapping out the native camera bayonet is the need for mounting exotic lenses, which very frequently have a short, sometimes even minimal, register distance.
The problem using a Nikon camera is that few brands have still longer register distance, thus most non-native lenses will not focus to infinity. Better to start with something having a much shorter register distance, for example, among the m43 models.