controlling tab size

I know that many people dislike tabs, but some people still find them valuable. I personally
prefer tabs over spaces for indenting source code because it is more semantic and easier to change
how wide the indentions are. I've had a lot of problems copying between files that used a
different number of spaces for indentions.

CCS3 Text currently says: A tab (U+0009) is rendered as a horizontal shift that lines up the start
edge of the next glyph with the next tab stop. Tab stops occur at points that are multiples of 8
times the width of a space (U+0020) rendered in the block's font from the block's starting content
edge.

Is there any hope of getting a property to control how far apart the tab stops are? The default
8em is much wider than I prefer. I would really appreciate a property like "tab-size" to control
this.

tab-size: 4em;