Yes, we should have a "Documentation" feature on this stack exchange.
I don't think it is very productive to say "let's wait on stackoverflow's version to mature", because the purpose of that functionality is going to constantly adapt to the needs of the programming community. It's never going to magically fit for this site just by watching it work on another site. At whatever point we choose to adopt the feature... there is going to be a great deal of adaption.
The general concept at a high level fits with this site's purpose. The point of this site is to act as a repository of knowledge for gaming. Creating full step-by-step articles would make the content more relevant and of a higher quality than purely supporting a Q&A format. Remember that the point of the "Documentation" feature isn't a replacement for the Q&A format, so both will co-exist.
It would be great to see this feature trialled on Arqade. Perhaps starting off with one of the popular tags (i.e. Minecraft?) and limiting the contributions to a select (and dedicated) few. I feel that regular visitors to this site will be happy to make meaningful contributions to some form of the "Documentation" feature.
In relation to existing game wikis (for which there will be some overlap in content) - the main problem with such sites is that they don't necessarily have the right tools to make improvements. Arqade users will have access to review queues, flag articles for improvement and a bunch of other tools to push the quality levels up.
Furthermore, having such features will help draw in experts of a game. For now, such experts have little reason to hang around on this site waiting on questions they may be able to answer. Giving such users the ability to document their experience without waiting on questions to answer would be a great way of sharing knowledge.