Someone know of a NCP "model" changer tool?

I was looking for a tool that can change an NPC model to a different one. NOT skin.
I intend to change models in the “Half Life 2” maps. Example: Maybe change the alyx model to Judith or something…Change a combine to a citizen…Change Breen to Eli or ANYTHING!
You get my point?
Does someone know about a tool of this kind? I would be so happy to have it.

Model Manipulator?