I wish this function were added.
It already happened to me that the Patch update fails and the files get corrupted. The Play button resulted into a crash.
I spent hours searching and editing some files in the game folder in order to force a re-download, with no result.
The only solution was to uninstall and reinstall. And since I downloaded the game, I needed to download around 9go.
It took around 6 hours because of slow connection.

That repair function should indeed be added, or at least a 9go installer you could download for once and for all, instead of an Installer which is, in fact, a downloader.
The sooner the better.