Thanks for your reply, Palal - very helpful.
It seems a bit risky still to go airside-landside-airside in 1 hr to catch the only flight of the day. I think we'll go with a safer option, luckily for BCN-JFK there are a few.

But we have been looking at Morocco for a trip at some point. Assuming flying into CMN and a private driver - is it better to connect at CMN for a quick flight to RAK, or are there attractions on the way between Casablanca and Marrakesh?