It's pretty unlikely that we will ever do individual parts export. As I explained before, it requires significant changes, and these changes will require changes in other places too. Besides, that is not the actual purpose and intended use for this tool.
To cut the pictures, it occurred to me that you can use the export png configuration to do this. You can set it to your desired resolution, then position the separated pictures above so that only certain parts are visible in the final output. Once you are happy with it, you can save the configuration as preset, say, something like 'upper leg left'. Do this for each body parts and limbs. Then when you need to export another character, you can simply load your saved preset.