While I am indeed jealous of schools that have fixed out of conference rivalries, OSU doesn't really have a "no-brainer" candidate. West Virginia would probably be the closest thing, but they should be playing Pitt every year. Pitt would be okay, but they should be playing Penn St and/or W Virginia. Notre Dame would be sweet obviously, but they have already been taken ten times over. Poaching that rivalry out of Michigan's back pocket would be satisfying, but highly unrealistic. Kentucky is Kentucky, so that one won't work obviously. Even though they are in the big bad SEC. Cincinnati would be okay if they ever find their way back into a P5 Conference, which is unlikely. The rest of Buckeye Nation would hate it of course, but not me.
I do find it aggravating that some schools have a perfect OOC candidate, but just don't schedule it for whatever reason. aTm-Texas, Nebraska-Oklahoma, etc.