AFAIK, currently there's not way to work at angles as easy as when you're aligned with the coordinate system.
You can create a grid helper, but the Front, Left, Top, ... keyboard shortcuts won't work with it. You need use workarounds with many other tools and modifiers too.
What if you could rotate and align the World Coordinate system to a surface?
Potentially with just one keyboard shortcut you could start working at any angle you want in the same way as with the original XYZ system.
There could be multiple World coordinate systems that you could go to at any time, as if you were changing from one camera to another.
As a reference to a script that intends to do that, not as versitile as if you could turn the whole ref system.
http://www.scriptspot.com/3ds-max/scripts/miauus-work-plane
