Nice idea Kidr, I wonder how that might work for digging out roots from small trees and bushes? I have been thinking of ways to get rid of stumps with my little tractor without trying to rip them from the ground with a chain. If you ever use it that way let us know how it works out. Your project sparked a couple ideas, nice job and thanks again.
DTS
I think a sub soiler would work very well at that if you used it sort of radially outwards from the trunk.
Then across the roots far enough out to be able to lift or split them.
Slow and tedious maybe, but not excavator scale cost of machinery.