Lots of insights on lean engineering in this interview to Elon Musk:
https://www.youtube.com/watch?v=t705r8ICkRw
3. Whatever requirement or constraint you have, it must come with a name, not a department. Because you can't ask the departments, you have to ask a person
[...] otherwise you could have a requirement that basically an intern 2 years ago randomly came up with off the cuff... and they're not even at the company any more... but it came from the, let's say, Air Flow Department!
4 Only the third step is to simplify or optimize [he seems to be off-by-1].
Possibly the most common error of a smart engineer is to optimize the thing that should not exist. Everyone has been trained in school that you gotta answer the question -
convergent logic. So you can't tell a professor "your question is dumb" - you'll get a bad grade!
So everyone basically - without knowing it - they got a mental straight-jacket on: they'll work on optimizing the thing that should simply not exist!