You can build as many safe guards as you like to mitigate landing with gears still retracted but why would anyone want to design a plane purely for crash landings when multiple failures (either of systems or system overides) would look to be the likely cause.
Douglas actually did that with the DC3, the main wheels projected slightly below the engines and if the starter motors were used to position the propellor blades correctly, an engines off gear up landing could be accomplished on a runway, with no damage whatsoever. The aircraft was simply jacked up and returned to service. I'm not suggesting it for modern aircraft, just a bit of aviation trivia.