Family Sharing seems limited
So instead of being able to share and play at the same time with any game makes co-op single player you take that away. Most games will make us buy a third party key because they want money for that extra computer being able to play. If we are going to borrow games from friends or family I think if the asking person is in the same network then it should be 100% shared and transfered to play together. If someone is outside the network then 1 at a time. No extra cdkey required. This is similar to trading console games with friends. If you don't pay a subscription fee its shareable. Thus it should be similar with computers since most of the consoles are going to start dying off here soon with the ♥♥♥♥ they are producing, and wanting to get rid of the trading option as well.