Ah OK, of course I don't say no to high res textures, I just would personally prefer 5 lowres textures over 1 highres one (probably similar amount of work?). Also, not sure how it would work out to combine highres and lowres textures.
BTW regarding your map, there are two ways to solve that problem that don't involve high res textures: 1) the way they did it in the original Unreal, projecting colored lights at the texture wall at some point, making a huge stone wall covered with the same not too big texture look pretty good. 2) Use huge textures (like 1024x1024 instead of the typical 128x128) so that repetitions occur so unfrequently they might not be noticeable as such any more.