Create possibility to cut not only as it is right now, centered on the draw path but also on the inside or outside of the path. The offset should be the diameter of the used tool.
Cutting inside or outside of the drawing in a geometry could be useful when doing cuts inside a board (slots, etc). In this way you just the draw the shape of the cutout at whatever dimensions you need and then you just specify “cut inside”.
Taking into consideration the tool diameter will allow to use not only one tool, but a couple of near diameters so you are not bound to one tool (if it is exactly “that” tool that you need to use, and you see that just broke you will have a solution until you buy another one).
It will be also useful if you don't want to use CAD software just for a simple front panel that you want to use into a case you are milling for that wonderful design you just finished. ) Making holes for encoders, pot's, connectors, LCD's and whatever.
Cutting outside it is also useful if you want to mill custom cases that fits together like Lego. You just draw what you need and don't worry about the end-mills that you have on hand.