By saying your lenses are those with built-in-motor, it means that your lenses are AF-S lenses. Being AF-S lenses, the Nikon D7000 DSLR will operate the lens as AF-S lenses (i.e. camera will do the focusing using the lenses' built-in-motor).
If you buy a lens with a built-in motor, it will not have the appropriate coupling to the camera body, so there is no way for the camera body to drive the lens' AF mechanism
I have yet to come across a lens with such a 'redundancy' feature built in.