Some things don’t change. Between 1973 and 1975 I cleaned out numerous B-52 Autopilot control panels that were gummed up with coffee, sugar and cream because the panel was the best place to put an open coffee cup on the center console. Cup holders are a great idea. The hard part is getting lazy pilots to use them. Even better - design the console with an slope so the cup won’t sit there in the first place. As for flight testing for something like this? Get serious! Flight testers have a lot more important things to do during a test flight and scenarios like this just don’t show up in the test plan. I’m sure everybody thinks it’s important right now but it is truly an outlier in the giant bell curve of important aviation events.