I am somewhat new to Stack Exchange, but one thing I have noticed is that the policy of not allowing discussion type questions is a very good idea. It helps keep Stack Exchange sites focused and to the point.
At the same time however, many times I have questions come up that require discussion. Something like "Which programming language should I learn first" is not appropriate for Stack Overflow, but could get a reasonably helpful answer on other forums like DreamInCode.net, Programming Forums, or maybe even Reddit. It seems like it would be more efficient to create a list of forums that we can redirect users with these sorts of questions to.
For example, instead of simply closing the example question above about a first programming language, could it be closed with something like "Stack Overflow is not a site for discussion based questions, but you can try asking about it on <'better-alternative-website'>"?
As far as the idea suggested in The fourth place: Polling, Recommendations and subjective-ish stuff, the idea would be similar, but instead of creating an alternative on Stack Exchange itself, questions closed as not constructive could include a "suggested place to ask" link, which would be specific to each Stack Exchange site (Raspberry Pi Stack Exchange redirects to the Raspberry Pi forums, Arduino to Arduino forums, etc.)