Actually gunners have pretty well stopped being infantry for the moment, and are fully involved firing light artillery in Afganistan.
The LM concept as a 'war winner' has been around for a decade at least, however, its only recently that technology has reached the stage where it can be 'low cost' (no doubt a relative term).
The advantages of LM over armed UAVs is that they can be in more places at once. LM will probably be fired from their box strapped to the back of a truck, no UAV landings, return flights, sortie rates, refuelling, servicing, etc, etc. You've got 50 UAVs, you'll be lucky to much more than a third of them in the air over possible targets. With LM you can have 50 over 50 different places. However, UAVs may be used to control some of them, particularly against targets in depth, where squaddies are a bit thin on the ground (but not entirely missing).
While the LM controller (or at least the guy who is told you've got a clutch of LM nearby, can hit whatever you want 30 secs after its picked) will not be an officer, he/she will have an officer nearby probably selecting the actual targets including running a quick mental check on what the lawyers said to ensure no war crimes.