If they can make it a little bit more robust, there would be a huge market for removing toxic plants. I was just quoted over $1000 to remove poison ivy from a 500 sq ft. wooded area of property. My satisfaction was not guaranteed.
Why use lasers when we can genetically engineer goats to hate the taste of corn/sorghum/wheat and love the taste of weeds?
Grazing animals would eat the weeds and naturally fertilizer the land. No harm if they don’t totally kill the weed, more food to fatten them up.
Granted, that's just a billion dollar idea. The multi-billion dollar idea is, as you said, to modify the animal and the plant together. The goats hate some taste in the corn, and the corn produces the taste such that humans cannot taste it. Maybe it'll ripen after harvest and the taste will lessen. I dunno. This way you can double-dip and charge the farmers on the new plant varietals and the goats. Bonus points if you can modify the goats to produce milk that's got vitamin-D in it or something.
I've seen this set-up in Victoria and SA before. The goats eat the grasses/weeds that grow in-between the grapes of vineyards. I've no idea if the goats eat the grapes every once in a while. The wine grapes are pretty sour and bitter to us humans at least.
It would be very 'green' overall.