Alright, bit of a breakthrough here -- after browsing through another pile of Panasonic IR config files, I finally found one with the ever-elusive TV input button! I have my fingers crossed that it will work.

However, all of the config files seem to agree on what the values are for the component and HDMI commands. There are no variants. So I have no idea why some of the input controls are working on one model, while others work on another.

In any case, Pierogi version 1.1.40 is now making its way up to the extras-devel repository. I've also taken advantage of this update to add the "Input" button to the Input panel, which upon reflection, only makes sense.