Block support and flexible layouts

One of the design factors of the MySite module is the deliberate decison not to allow users to add blocks to a MySite page. The logic is that the Blocks module already support user customization, so showing blocks in MySite is redundant.

But, if we could remove the left and right rails of a theme, where block are normally placed, then it might make sense to support Blocks in MySite. In that case, MySite would be used to give the user their own configuration of blocks and content. That would be cool.

By design, the 'Layouts' in MySite can invoke Drupal themes or not. The original plan was to use custom Layout files to bypass the Theme engine entirely.

With the release of Gutenberg, though, I added theme swtching to MySite. http://drupal.org/node/124408

This begs the question: should we support MySite theme pages that are stripped of the default rails, so that the user decides which content gets on the page.

I think the answer is probably yes, and there are two obvious ways to do this:

1) Use the Layout files and expand the available selection of layouts. This might mean dropping support for Theme Switching.

2) Use PHPTemplate to our advantage by creating a custom page-mysite.tpl.php for each theme that includes only the default elements that the site designer wants on every user's MySite page (header, footer).

Some fallout from the decision would be:

A) In MySite HEAD, support for 'layout regions' is added. Called 'positions,' these elements mimic the regions in PHPTemplate themes. Instead of using 'positions' MySite could, theoretically, overwrite the existing theme regions being sent to PHPTemplate. I'm not crazy about that idea.

B) Site maintainers (or theme developers) would need to create a page-mysite.tpl.php for each enabled theme. The MySite module would only include a version for the default Drupal themes.

Feedback welcome.