[css3-value] calc and child selectors (was: Proposal for Touch-Based Animation Scrubbing)

Please disregard if this was already brought up.
While looking at Tab's proposal for an image carousel, I saw the following
idiom:

*.carousel > img:nth-child(1) { animation-delay: 1s; }*
*.carousel > img:nth-child(2) { animation-delay: 2s; }*
*...*
*
*

Could this be replaced with a new keyword for calc()?
For instance, if you want all the images under .carousel to turn one by
one, you could write:

*.carousel > img { animation-delay: calc(nth-child * 1s); }*
*
*

This new keyword would only be valid inside a child selector and return the
sibling order.