You could do a mass-replacement (if I remember correctly, you can do that in Noggit ?), but also you could replace the texture in your files. Another option is changing each adt to use your texture instead of the previously one, the last one is a bit tricker though.
1. is just what you did not want to do. Fly around and use texture swapper for swapping texture A for texture B on whole ADT, and do all of this manually for whole map.2. is basically just overwriting BLPs of texture A in Tileset/.. folder with BLPs of texture B. This will, in fact, give you 2 completely same textures in your MPQs, so you will loost option to use current texture A forever, but you won't have to edit ADTs.3. I don't know what he meant by this at all. Some mass scripted file-structure editing, I suppose. I have never got to such techniques.
1. I remember there is a function in an older noggit version (1.1 ?) that allowed swapping textures on an entire adt. I meant that one. I am not sure if current version features it, I am not up to date.
