Provide simple way to export images optimized for the web

I often use inkscape to create website interfaces. But exporting things in inkscape works fine only at 90dpi, when i try to reduce it to 72dpi exported images are stretched accordingly.

Rather than change the default export tool, my proposal is to introduce some specific features to export optimized images for the web.

I'd like this workflow:
- Mark groups/elements for export (very simple: just add an attribute to xml)
- Create sprite images
- Mark groups/elements to be exported together in a sprite image
- See/copy css for sprite image
- Select export for the web ... from 'File' menu
- In the export dialog select which elements/sprites to export and where
- The images exported are optimized for the web using some tool like pngcrush (not only 72dpi)
- maybe necessary css code could be exported along with sprites also

Implementing something like that and correcting some other little problems should bridge the gap between Inkscape and Ilustrator or other commercial tools in terms of website interfaces design