If you run into restrictions on booking an open jaw try this:

You want to fly CLE-FRA and then return CDG-LAX. Say you are getting married in CLE.

Book the CLE-???-FRA flight and then book the return CDG-LAX and then book the first flight out the next day for the LAX-CLE portion. They will usually let you do this.

While yes this is throw-away ticketing, but everytime I have booked it the agents did not seem to mind even if the flight to LAX is out of the way.
This way you don't have an open jaw on both ends of the trip.

BSL