Im not sure what the problem is, i didnt quite understand, but i usually make a texel a single unit, and use quite large scaling.
Im actually not sure that it matters tho, it just depends on how you adjust the zbuffer (near and far clipping planes) in the projection matrix.
If you stand on about 1024x1024 texels to touch arms outstretched with another guy, i guess thats about good detail, which helps with the
"apparent scale" that youll see with your eyes, but more detail is always better, but if you can get to about 1024x1024 a mans personal space square
I think thats quality detail. the more detail... the "larger" the world and the more correct itll look, cause remember we see a different colour every element
to the eye... if you look at some of the new voxel stuff out now youll see the scale is more realistic because every element is a new voxel.
[EDIT] the actual size of the map doesnt matter, most gamers would prefer an infinite world, no? it just depends on how much you are willing to model [/EDIT]