Upon defection of a click-through license (probably doable, given the formal language of legal contracts), examine the text for arbitration clause with opt-out text, and pop up a little dialog or sidebar that says "click here to opt out of the arbitration clause". That might require manual identification of how to do so initially, but I could imagine building contract signatures so that the process could be further automated for others.
What's preventing the companies from then simply dropping you as a client?
No idea. But I assume that if a contract has an opt-out clause, then it should be possible to do so without voiding the rest of the contract.