Why not use a martini shaker, non-melt ice cubes, and cold milk? Cold foam; only a few seconds more effort. Maybe even sweeten the 'foam' with a tiny nip of simple syrup, vanilla, etc. (if you carry syrups) as a small specialty up-charge.
I love the idea of shaking the iced drinks. They always seem to lack something so I only order them once a year or so. Then im reminded of why I dont really like them and then spend the next 15 min chewing on the ice. ANYWAY im going to give the "Shaken Iced Latte" a try.
I have always been under the impression that it is a health hazard due to the difference in temperature between the two substances, increasing the potential for growth of bacteria on the surface of the beverage. We have completely stopped putting warm foam on top of iced beverages.