In the discussion in MDL-32412, where it was proposed to use a percentage layout based on Matthew James Taylor's 'Perfect Holy Grail (Percentage) Layout', Martin made a comment from which I would like to quote:

"...Based on a quick read: if the issue here is that the base theme

needs fixing to make it work better with RTL, then let's fix/replace

the base theme. I don't think adding a new separate theme sounds

like a good idea. It was already made confusing enough with the

introduction of Canvas..."

In line with Martin's comments then, I would like to propose that BASE theme layout is change from PIXEL to PERCENTAGE for Moodle 2.4 and than all NEW themes can be based on this new layout.

The Perfect Holy Grail (Percentage) Layout uses less divs than BASE and is more versatile, it contains No CSS hacks, is SEO friendly, contains no images, no JavaScript and is Cross-browser & iPhone compatible.

Current CORE themes, whose parent is only BASE, could be converted to use the new layout. Whereas CANVAS theme could carry the old pagelayout.css from BASE while at the same time excluding the new new pagelayout.css from BASE theme, thus making those themes, whose parents are bother CANVAS and BASE, benefit from this and so will NOT need converting to the new layout since it will not affect them.