Hello from Linz, Austria where I am speaking about CSS Grid Layout tomorrow. Before I left I did some experimenting with
display: contents and you can see a link to a write-up of that and some code examples below. I'm going to follow that up with some thoughts about the method as used with CSS Grid Layout.
On my return to the UK, I will be getting things lined up for the launch of my CSS Layout Online Workshop - if you are interested in the launch offers or to find out more about that take a look at the site, and sign up to be notified.