Hi Wout Martens ,
Thanks for your feedback.
You should be able to use Spotify Connect with Google Home.
For the other points you mentioned, I can't provide a date at this time but we'll definitely look into this integration in 2019 as this is one of the most requested devices by the community. If you haven't done it yet, I invite you to vote for this request and to follow the topic to get notified when the status is updated.