I have vast patches of what I think is knotweed. Herbicide control is not practical for me because I have certain blood ailments which can be worsened by exposure to such. Owing to the long tendrils of this weed, it seems to me that a rotary "comb" (horizontal axis) could be used to expose it, then a v-notched side-to-side blade could cut it off reasonably close to the ground (lawn height) while it is in tension. This obviously does not destroy or kill the weed, but certainly could be expected to tame it. Do you know of anything of the sort already available?
Keeping it from seeding can help control the weed.
I'm sorry I don't know of such a tool.