Beyond that for in-row weeding a engraving laser on a Delta: https://github.com/Agroecology-Lab/Open-Weeding-Delta/tree/m...
Or if I'm feeling rich by then this third party weeder looks pretty good https://github.com/Laudando-Associates-LLC/LASER
In my head it's £3-£5k, so by the time it's useful probably a bit more than that.