I am having trouble thinking what would be beneficial to be laser trimmed in a finished product, let alone how you would go about doing it or determining what values would be most ideal. Sure, laser trimming is extremely useful when building a component, especially in ICs, but are you really going to do something like buy a prebuilt DAC, remove the top of the chips, and trim the ladders for greater precision? At that level of reverse engineering, just build your own gear.