A few tips:

Ask your airline not to mention a specific airline and flightnumber on the ticket in case the route is flown by several ZED carriers, that way the only endorsement on the ticket is 'valid all zed carriers' and nobody can refuse you because the ticket wasn't issued for them.

Also, although I know the route on the ticket should theoretically match the sector flown, it seems some airlines will also accept a ticket issued for a different route if the fare is the same or higher: LH for instance does it standard: never had a problem getting on a FRA flight with my MUC ticket, although I understand this not to be the norm.