We have considered this in the past, but the Rhodes Ferry only runs from 9.00am going to Rhodes from Fethiye and back at 4.30pm to Fethiye. So the flights into Rhodes would have to be timed to get the ferry out, or there would be an overnight stay, plus the flight back would have to be in the afternoon or evening to match up with ferry times. The other thing to consider is the ferry has been cancelled in the past due to bad weather and mechanical faults. We have been to Rhodes from Fethiye to stay over for a couple of nights and going over we were the only people to be singled out and have our suitcase completely searched by the Customs, this was because everyone else on the ferry were day trippers with no cases. I think the Customs must have been looking for something to do.
Good luck anyway and if you would like the name of a super hotel in Rhodes with uninterrupted views across the harbour (ideal for a honeymoon)let me know.