ok, i understand. but have you tried with gatherbuddy and grindbot? gatherbuddy should allow you to 'loot mobs'. and maybe the code is already written in gatherbuddy to harvest the mobs. since the purpose of gatherbuddy is to harvest anyways.
otherwise, look for a plugin. a plugin would allow the bot to identify when a mob was present that needed harvesting and force the bot to harvest it.
and ofc, you can always write your own plugin. there is a handy guide to writing plugins here on the forums.