Grid Layout Level 2 Ideas

We want the ability to collapse grid tracks (similar to collapsing flex items or table rows/columns), but we're not sure exactly how to do it. One attempt:

Specifying visibility: collapse on a <a>grid item</a> causes it to become a <dfn export title=“collapsed grid item|collapsed”>collapsed grid item</dfn>. This has the same effect as visibility: hidden, except that if all the <a>grid items</a> spanning a track are <a>collapsed</a>, the track's [intrinsic]? size becomes zero.