Your development request is not likely to get any support as, AFAIK, there is no real demand for this and no Discourse customers are asking for it. So I suggested options to expose wiki posts in ways that can be achieved already.
Another way may be to tag wiki posts with word “wiki” so you can yet put your wiki post in any category and search all wiki posts with that tag.
You need to tag wiki posts manually.
May be in future releases the system could tag wiki posts with a wiki tag automatically in order to make them easy to search for. It should be easy to implement.