When cutting any wood with a CNC router (especially open grained wood like walnut or mahogany), I find there is a high risk of pullouts when the tool is cutting across the grain. Pullouts are pits in the surface created when bits of wood are pulled out by the tool rather than cut smoothly.
My work-around has been to slow the whole cut down, take several finishing passes, and use very expensive and sharp tools. But wood can vary a lot from piece to piece. So, I might think I've got my tool path locked down, and then a piece comes through with a looser grain system and I get pullouts again. These pullouts can ruin a piece if they are too deep to be sanded out, which can be depressing if it happens to a $300 piece of curly walnut.
I would like to be able to slow the feed rate when the cutter is moving ACROSS the grain. This feature would be very closely related to Maximum Directional Change. I would implement it as another line in the Feed Optimization menu by having the user select a reference line or edge that runs parallel to the grain of the work piece and then enter an angle of motion (or angle of tangent if on a curve) relative to this reference beyond which the Reduced Feedrate is used.
This would be very useful to woodworkers, who always plan the grain direction early in the design process. Even plywood would benefit, because the top veneer can be particularly weak and prone to splintering off when cut across the grain. This would also be of interest to anyone cutting any composite material that has oriented reinforcing.