[css-grid] :nth-row, :nth-column selectors and similar

All,

Are there any active proposals (or any that have been shot down) regarding
table-like selectors for CSS Grid? Namely the following:

- nth-row
- nth-column
- nth-last-row
- nth-last-column
- first-row
- first-column
- last-row
- last-column

These selectors could prove incredibly useful with `auto-fit`, and
especially once subgrid is implemented.

The use case would be similar to that of tables, but for cases where tables
are not necessarily appropriate to be used.

The one problem I can think of: how will elements that span multiple tracks
be handled? My naïve solution would be to use the top left cell, though
I've no clue on the benefits and drawbacks from such.

jhpratt