Output format argument for meta directive

Hi,

I've been working on a set of transformations of reST to various output, 
most notably to reveal.js-based slides (I have a repo at 
https://github.com/rartino/httk-rsttools - but it is still very much 
work in progress.)

In the 'Directives' documentation file, the meta directive is presently 
the only implemented directive under the 'HTML-Specific' headline and 
its description is indeed very HTML-specific.

I have multiple times found myself looking for a way to include metadata 
in my source documents for use in other contexts and for other output 
formats, and thus found the HTML-only nature of meta inelegant.

Is there a reason the 'meta' directive doesn't take an output format 
argument, making it possible to use it for meta-data in contexts also 
outside HTML? I.e., to make it work much like the argument to the 'raw' 
directive, e.g.:
   .. meta:: pdf

Is this something that could be considered for inclusion in the reST 
standard?

Best,
Rickard