Is there anything like this out there? It feels like there's a more generalized class of problems that this falls into, where consumers are placed in a suboptimal default state, and opting out requires some minimal but non-zero amount of effort. Sort of adjacent to the "call Comcast every 12 months to renegotiate my cable bill" problem (for which services already exist). Are there similar unsolved problems that fall into this class that could be addressed by a single service?
I suppose you could notify users based on inbox activity if your could coorelate arbitration notices to inbound emails through domains and their integrity into (DMARC, etc). Check out the newsletter app Meco for what the UX around their Gmail integration looks like.
Also, consider contacting the FTC and filing comments that instituting arbitration requirements should require reporting to the FTC or other agency; you’d then have a central source of truth to crib off of.