Windows Store games are now playable offline with a bit of work
 

While game services like Origin, Steam, and GOG allow for playing their games offline, Microsoft's Windows Store has lagged behind its competitors in this respect (along with plenty of others). However, after it made some improvements to the Windows 10 Store, Microsoft has posted instructions for enabling offline play of games purchased there.
http://techreport.com/news/30896/win...-a-bit-of-work