I think it would be a helpful feature request. Logically, it would make sense for the crosshairs to use the format associated with the axis settings.
As increasingly the graph builder becomes the platform of choice the use of the graphics toolbar becomes increasingly painful. There was a time where C would give me the crosshairs, Z the zoom tool. Now the column listbox within the graph builder picks up the focus and prevents these keyboard shortcuts from functioning.
Dave
-Dave