Initially keep it simple; Mechanical for between row weeding. I'll probably start strapping a couple of these to some linear actuators: https://www.getearthquake.com/products/fusion-drill-powered-... (they work surprisingly well)
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
What's the plan for using an engraving laser in open air without blinding a neighbor? Does the bot fully roll over the target area before firing or something?
I sometimes help out at a hobby vineyard of 0.7 hectare; weeding in the row is a lot of manual labour. Your platform seems like a good fit. I like tinkering and robotics, what kind of price point are you aiming for?