Awesome idea! Beats me out walking thousands of feet back and forth with a much smaller version on a handle any day...
It does give me some thoughts though. I think a FEL mount might likely work better. The way it is you either need to go backwards or drive over the nails and other tire hazards you're looking to prevent. Doing it on the FEL allows you to drag your harrow at the same time as well, this makes your first pass while preparing for the second pass all at once. I think I would create a mount at the back of the FEL bucket near the bottom pivot pins or the lower QA locks so you can use it with the bucket turned up, and still be able to turn the blade edge down to perform other small tasks along the way (pushing a stone or something out of the way).
If you can't tell, I plan to "borrow" your idea with some minor alterations
Thanks for sharing! Hopefully you like and can use the ideas you put in my head...