Speaking as a designer - usually we'll have looked at every possible option to meet the requirement, proposed several to the customer, and either they or the end user turns around and says that, actually, they'd rather just hang people off the side.
OK, I design ships and not aircraft, but I've had conversations that weren't entirely dissimilar. Very often, it's the designers and the end users teaming up to persuade the customer that just because something is cheap and proven doesn't mean it's actually good. On one occasion, I was running a meeting where the end user suggested that, if the customer thought a particular solution was acceptable (it wasn't!), then they should be the first ones to try it out.