Mazda 6 2017 Problems

It's hard to give you a definite recommendation, as most cargo measurements are in litres rather than floor length, but I reckon most mid-size wagons and large SUVs would do the job for you. 

Most of these have a flat boot floor with the seats folded, and likely have ample body length for sleeping. 

So Mazda6, Skoda Superb or Ford Mondeo wagons are worth a look, plus large SUVs like the Mazda CX-9, Kia Sorento and Hyundai Santa Fe. 

Don't be afraid to try them out for size at the dealers either. You'd certainly test out a mattress before buying right?!

All of the cars you name meet your criteria of size, economy, performance and handling.

You could also add the Mazda3 and 6 to the list.

Of all of those I would nominate the Camry as the great all-rounder.