This is implemented in the next release. Since it is not possible to store anything on the index, it works similarly to the Create drop-downs in a book, category, etc - offering all the routable content-types the user is allowed to post in the wiki.
This required creating a base template for the wiki index (there was none before) that the links could be inserted into. With the new template vw_area_index (by default containing the create links and the area tree), it is now possible to customize some wiki index blocks easier using the style system.