I read with interest the article in MEW 259 about upgrades to a pillar drill, in particular the attachment of laser cross hairs to indicate drill position. The point is made that the crossing point "probably isn't fine enough to use on milling machines". Having no experience with milling machines I'm not sure how much finer the lines would need to be but wonder if there is scope to attach small lenses to the laser housings to give finer focus (and maybe collimation) of the beam at the distance required and thus improve the fineness of the crossing point.
An obvious downside to this would be the likely need to refocus at every change of distance (though collimation, if possible, might reduce this problem) with any inherent inaccuracies in the position of the crossing point that may be introduced.
I'm sure there are people out there that can add some more 'engineered' thinking to this idea 😀