I am super excited about the Farmbot and will be integrating it into my hybrid aquaponics system.
Two things that I see with the weeding tool where I see improvements could easy be made:
#1 The weeding tool needs to be longer so that you can work around plants without damaging them
#2 A plunge and spin system tool that extracts the weed and then has a plunger that pushes it out of the extractor would be an easy type of tool to make. Here is a link to a video of a tool of this type. One could be made using a solenoid as a plunger and a stepper motor for the rotation. If it was mad 18" long it could easily get between plants.
This video is only so visually represent the idea. https://www.youtube.com/watch?v=eq3BCPC5UhY