If you want to keep small details, for whatever reason, you can attempt to do so using detail preshading. Look at this...
The left is v1.8 of my Finnish StuG III texture. The right is v7 of my Finnish StuG III texture.
Ignore that the second one is brighter than the first one. The second one is under fullbright settings, the first was not. I want you to look at how the details hold up. The scale down doesn't do it justice, since the details are pixelated due to scaling the static image, rather than a dynamic object, but you can see them clearer even with the poor resize on the right.
At least you can see that there are details on the one on the right. Note that the texture is a 256 so I was dealing with a very limited space. You have subtle contrasts on your textures... subtle contrasts are what you see on the left example. On the right you have less subtle contrasts, with an artificially bright border against an artificially dark border creating more visible details at zoom.
I think this, combined with simply reducing the number of colours/increasing general contrast/using very dark and very bright regions/increasing the size of colour regions/increasing the size of greebles will help the long distance visibility of your textures.