As a Site Manager I can use Customize Site to change the display order of the Site pages so that the first page in the list is the default page that gets displayed. See screenshot attached.
Note: Saving the configured site pages (as in OK on the Customize Site page) will show the default page)
Secondary Story: As a Share Developer I can create a custom page that can be used to as the landing (first page) for a site rather than the site dashboard. have a custom dashboard. There's no additional code expect around this use case, its an additional story that we can support by making site dashboards optional.