Bad Design in Star Wars
blogs.amctv.com
blogs.amctv.com
http://www.somethingawful.com/d/news/nardo-design-empire.php
(That may not be the original link, but it was the first result on google.)
How do you know they didn't? Predatory consultants and contractors absolutely flourish by hanging off the underbellies of large institutions. Somewhere in the Empire, some corporation is billing $450 per replacement blaster trigger.
People will find a way, intentionally or not, around your defensive design. True for code and military engineering alike.
As technology, yes of course there are loads of flaws, Dr. Who's Darleks must surely be the classic though. As far as movie design and art direction goes, John Barry the Production Designer spawned an entire new genre of sci-fi style.