Our proprietary engine uses same texture/material for LODs. When I try to export as multiple LODs I can set different size for texture. But there is no option to merge into one UV. I can only do that, if I don't make LODs. Is there any workaround this. Or is this how software works?

example: What I need.
Lod1_texture1/ material1/ UVmap1
Lod2_texture1/ material1/ UVmap1
Lod3_texture1/ material1/ UVmap1