If you try to move a page to a name that already exists, there is an error page :en:MediaWiki:Articleexists, but it does not contain a link to a target page. I believe it would be useful to add a parameter $target with the target name, so that the link can be added.
The reason why we need such a link is that sometimes there is a problem: if I would like, for example, to move :en:Russian Empire to :en:Russian empire, then I can not just enter a target name :en:Russian empire into search field as it will be automatically corrected to a name of the existing page :en:Russian Empire, thus I should do more actions to open this page.
The idea of such a link was approved on Russian Wikipedia's technical forum, see :ru:ВП:ФТ#Переименование в существующее название.