I've used this to bake all the materials (each model had a different uv map name) into a new lowpoly with only 1 material. Basically to bake the maps I have to join the models, but after you join, only 1 UV map works, so, 1 model will have the correct UV map, while the others will be 00. Copying pasting made sure I was using multiple materials, like you'd usually use, but with the same UV map, which in this case where different names and usually won't occur. I'm not sure this is used outside of what I did, but maybe someone else will get into this situation. I had only 8/9 UV Maps, maybe tho with more it's more time consuming.