You can get this effect by using a masked material and then using ScreenPosition to check at what pixel fragment is. If it is inside this band of pixels you dont want, then set the opacity to 0 and it will be removed from the render.
HTH
Then the only answer left is to preset the depth buffer to 0 on the pixels you dont care about. Still, I am not so sure that the performance loss of using a masked material vs using a non-masked material is that great, but GL.
How would a dev go about controlling rasterization?
Specifically, can I skip a pixel or a whole line across the screen from rasterization? This is specifically for better performance (rendering less than “1080p” in a “1080p” frame, or w/e resolution).
Thanks in advanced for any responses! 
masking a material in this fashion would degrade performance.
I should have stated this is for performance reasons. Thank you for the answer though!