How? I suppose the most effective way is to have those proxies attack each other. But don’t, it’s likely illegal.
The hard part (and it truly is hard!) is convincing a few companies to do this. It risks user complaints in the short term, to solve a problem that may not be very acute for the largest companies (who can simply absorb these attacks).
(No I don’t expect any response but I am just leaving this thought for those who stumble on this thread in the future).