This would be a good idea for those without tilt.
I thought it might be possible to at least add a shortcut for incrementing/decrementing angle with a plugin, but setting the angle is not exposed to the python API.
If it was, making a script/plugin as a temporary workaround would be trivial. Even for those of us with tilt, it is useful sometimes to change between 0 and 90 degree brushes or increment in x degrees.
I did a bit of research and found this post: Modify Brush Angle . It unfortunately looks like it’s a bit more complicated than it seems because not all brush engines have an angle property.