Nice! let's talk about our "wish list" and opinions.
1. I love the idea to have the 'topnav' block position by default, and also a default 'extmenu' or 'menutree' block assigned to manage the Theme navigation by default, instead leave it to the theme templates.
2. 'leftnav' is needed for some specific cases, but may not completely necessary and it's better to apply an specific template for the block as you say.
3. Breadcrumbs toolbar is excellent. We may assign different config vars to each toolbar: one for enable/disable breadcrumbs, other for search, other for font-resize, and i want a width-switcher too.
4. i think that the minmax.js works good in the latest version of YAML
5. Required backlink to YAML in the footer and information updated in the changelog.
6. Yup. A default 'extmenu' (single level) by default would be good, and a 'menutree' for multi-level nav-menus.
7. I think that the images and all that stuff is for designers. We should leave
BlankTheme as simple as possible to understand it with ease
8. Nice idea. At one side of the YAML backlink.
9. A designer matter again. Background images will be easily customizable, and we can include a topic in the manual about it.
10. It's possible to include different color schemes, nice

. May be in the same way as we can switch the style to switch widths (flexible, fixed, minimal).
11. The admin menu is a fixed plugin. Order the common tasks of an admin, but still doesn't check the availability of the modules. Noce point

.
Include some fancy stuff to it is a nice idea too
12. Let's contact to Dirk Jesse and ask him for the builder.
13. Graphical layout borders (gfxborder) can be a "
BlankTheme" distro

.
Let's keep as simple as possible.

let's work!
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Mateo T. -
Mis principios... son mis fines