Something that would help move the work on robotic sensors and manipulators for agriculture forward would be an affordable, robust platform on which they could be mounted and transported through a field. It seems to me that self-propelled sprayers with high clearance and adjustable track widths, intended for row crop operation, offer the best model for such a platform.
Note that these machines are not built for traction, but to suspend a load high enough that it doesn't interfere with crops. This and the adjustable track width is why, taken together as a class of machines, they make a good model for a robotics platform.
Ideally, only the frame and running gear from one of these designs would be used. To that add a transverse beam (gantry) along which suspended robotic modules can move sideways, mounted far enough above the ground surface to make room for the modules and to avoid interference with the crops.