^^ I do this all the time. Really need a powerful machine to make this happen, depending on your configuration. I'm at 15 layers of full HD using this technique.
7 layers for main video/logo/effect mixing on main screen
3 layers direct to columns using layer router "composition"
1 layer extra widescreen (3840x1080) for full room video between main screen and columns
3 layers for slicing a large LED a few different ways
1 layer for full screen of large LED
Most of the layers for slices (7) just hold cameras/layer router and text stuff, so I'm really running to much at once.
Usually mix 2-4 layers only, not the full 7, most of it is just for holding content