Without making it particularly sturdy, it was able to lift 4 kg and has a pretty good movement repeatability even if totally "blind" (I am currently working on its vision system), two things that drone would have a hard time duplicating in outdoor conditions.
I can PM you later when we have all the things set up if you want. Or we can just chat here.
In order to make the system mobile I'm making a sort of tiny tractor that relocates the bases of the support struts (I use a tripod.) You can have separate symbiotic fleets of static "heads" (tripod+wirebot) that are moved by mobile "rovers".
This lets you optimize the system a little better, since most of the time the head units will be working and largely stationary, so a small fleet of rovers could be enough to handle a large fleet of processors.
For ricefields I think you might sink stepping stones in a triangle "grid", maybe concrete cones about a meter long and 10cm at the base, inverted and stuck in the mud. The distance between them would be fixed by the span of the suspended robot.
You would also want "vascular" conduits to transport material to and from the working heads. These aren't necessarily physical tubes or conveyor belts, they could be made of simple cargo drones like streams of ants.
You could make bridge or rail units that fit between the stepping stones for temporary reconfigurable transport networks. (If your cargo drones are sure-footed and reliable these could be simple planks.)
Also, have you heard of Hangprinter? https://vitana.se/opr3d/tbear/ (I have no affiliation w/ it.) It's a "RepRap hanging from the ceiling"
I don't think any rice farmer would like to put concrete blocks in their fields unless every task is reliably automated: they depend on machines to prepare, plant and harvest the rice and a stone in the middle of a ricefield would make these steps harder.
I know that there are several projects using wirebots for 3d printing. It usually allows for a bigger printing volume than regular CNC-like designs, and I think they must be able to have a high precision too. I am wondering what is the limitation there.
Do you have any contact info?
Passing tools among a neighboring system is going to be hard as there is a "dead zone" bordering the rectangle drawn by the pole but there may be a way to smartly cross the wires so that two system may share an area where they could pass around tools.
Harvesting is actually, counter-intuitively, a low priority task IMO. This is usually a single day of work, and this is the one with the highest stake, where things going wrong can jeopardize your whole harvest. People will want to be present for it I think.
What needs to be automated first are the tedious tasks that need to be done repeatedly : weeding, monitoring, watering.
About harvesting, a farmer friend proposed something interesting: just pass bags/baskets from the field's side to the place when the human is inside the field. Ricefields are very muddy and if you work in the middle of one, doing back and forth to the border is really tedious.
Imagine being able to plant, weed, and harvest strawberries from a center pivot. Huge.