Please consider providing "Do not recompress unedited JPEGs" option in export/publish controls when export/publish "file type" is set to JPEG.
This would be useful when exporting or publishing (as high quality JPEGs) a large set of files that is a mixture of raw files (edited in LR) and JPGs that are not edited in LR. Currently, all files get compressed during the conversion to JPG. This means unedited JPEGs get unnecessarily recompressed, wasting time and quality (and energy, if on a battery powered device).
The reason someone might have "unedited JPEGs" that they don't want recompressed is because they may be high quality JPEG exports out of another application (e.g. Canon DPP or Nikon Capture NX2), that have been imported into Lightroom.
Another example is when someone wants to keep all their "baked in" changes to an "externally edited" image, but doesn't need (or want) to save off a huge TIFFs of that image, and instead will just keep a "finished" JPEG.
Right now, the only way to ensure unedited JPEGs are not recompressed is to create two separate publish services: one for unedited JPEGs and another for everything else. That is messy. Having a simple "do not recompress unedited JPGs" option would take care of this for those who care about it.