From my experience, whilst some garments can be a little fiddly and tricky, especially when in a rush, and a little desperate after waiting in a long queue, providing that they have either hook and eye, or press stud fasteners in the gusset it is not too bad. Most bodysuits and pantie corselets have either of these. I love jumpsuits and playsuits, but the biggest problem wearing one for me is exactly what you have just said.
However in my experience, by far the worst garment and situation I have ever encountered was on a winter trip to Lapland hoping to see Aurora Borealis we had to wear very heavy and tight fitting thermal all in one suits, and big thermal lined boots. At minus 35 degrees, they were very much needed.
There was just one toilet on a mountain top, and you had to walk as best you could , in complete darkness, as it was 01.00 am, for a few minutes to reach there. The queues were very long, ( including the men's) ,due to the time it took to get out of the suit, and back into it on top of your own normal clothing, and obviously with it being just one cubicle. I can assure you that due to the extreme cold, and the lengthy queues, and time it took to get out of the thermal suit, it was quite a traumatising wait. !!