More granularity for font-weight?

Hi,

Currently CSS font-weight can take a few fixed number values: 100, 200,
300, ..., 900

It was brought to my attention that fonts with intermediary font-weights
seems to be more common lately:
 - Roboto and Noto Sans CJK have a 250 thin font variant
 - Apparently Windows has been shipping with 350 semi-light fonts for quite
a while now:
    - LeelUIsl.ttf: Leelawadee UI Semilight
    - NirmalaS.ttf: Nirmala UI Semilight
    - segoeuisl.ttf: Segoe UI Semilight
    - seguisli.ttf: Segoe UI Semilight Italic

I have been floating this around to a few folks to gather initial feedback.
Notably, Bram Stein from Adobe investigated the behavior of different
browsers when presented with non-standard font-weight values:

   "I’ve tested on all browsers I have access to (IE6+, Android 2.2+, iOS
4+, Firefox, Chrome, Opera, Safari, BlackBerry, etc.)
    and all of them fall back to “normal” when they don’t recognize a font
weight value (in either @font-face or by itself).
     My test case is here: https://github.com/bramstein/font-weight-test"


Should the restriction on font-weight be relaxed?
 - all positive integers?
 - all integers between 100 to 900?
 - add 50 increments between 100 to 900?

Best,