The 3rds feature is great, whilst one could argue that upper middle and lower 3rds are possible with custom snap areas, it's both clunky (on multi monitor setups the window subject to snap flashes on other monitor) and messy( having coloured opaque windows is distracting to work flow).
Any idea if this will happen or indeed custom snap grids could be. defined in settings as relative co-ordinates/percentages of screen height/width?