I have seen a few questions that sound more or less like a full design problem description. In essence the poster is asking somebody to do the work for him.
Now the question is when does the question move over form being interesting/filtering your options? When do we wander into the land of actually needing to consider instead billing the user (when do we say ask a consultant)? For example asking for options that exist is one thing*. Asking us to choose from said options is really the job of the engineer. As is enumerating the options.
So how far are you willing to take it. I'm all for asking. Just wondering why I would answer a question that I get asked every 2 months and get paid 1000 euros for my effort**? Are there any guidelines?
The problem as I see it is that there are less parts in mechanical engineering than code. Everything is just more coupled. So the questions are much closer to the whole problem than specific programming questions.
* Asking for an authoritative list of everything that exists is a bit too much asked too.
** In fact I do think engineering disciplines would benefit from more openness.