A little workaround here is to delete the “@robmeade closed this topic” post. Then the first post is the last post, and any edits would bump the topic.
Personally I think it would be a cool feature. It’s not on any official roadmap right now, but there’s a topic here:
I think a lot of communities do this by having a category dedicated to wikis. On meta we have howto, where a large number of topics are wikis. You can toggle the category setting so that all new topics in a category are automatically turned into wikis.
That said, I think a URL parameter for wikis is a reasonable feature request. It could function like ?status=open. Then it would be easy to add a tab to the top menu.