Geometry of Cover

[icefractal]

Looks similar to the 3.5E D&D cover rules, except in those you get to pick which corner to use, so Yuji could draw from the NE corner and have partial cover (and that confusingly, a line tracing along a parallel wall counts as partial cover). I think it'd work fine, but IDK if it's as much more streamlined as you'd want - it still requires tracing 1-4 lines on a grid.

If you do decide to do just a single level of cover, you could go center to center. In this case that would be cover for Yuji, no cover for the other two. It reduces it to a single line to trace, and avoids questions about which corner to pick.