If I showed the bright orange suit to my wife, she would order me one tomorrow, just for spotting me on the slopes.
Best time for a onesie is when you have slopeside ski in ski out lodging. Just kick off your boots, step in to fuzzy slippers and drop the onesie stepping out with your lounge pants already on under it. After dinner, step back in to it, boot up, and back out the door for the night session.I liked skiing in my old Chlorophille GoreTex onsie shell that was a good fit but hated going indoors and unzipping and having to wiggle out of the top and then having it hanging off your hips. More wiggling to get it back on.