A progress update, while we are getting closer to Mosaic 1.0b1.
The first beta will take a few steps back and focus on content area layouts. Site layouts (main_template replacement) will be hidden behind a zcml feature flag.
TL;DR; Mosaic 1.0b1 will cover two to three use cases:
1) TTW type views: predefined centrally managed tile based layouts can be assigned to content types and selected by user through Mosaic Editor (similarly to selecting legacy views through display menu); these centrally managed layouts mostly "static", but users may re-configure tiles in them per content when necessary
2) inline editing: Mosaic Editor provides inline editing for most text based fields (and more should be implemented later)
3) free content area layouts (by selecting a predefined centrally managed layout and customizing it – obviously making it no longer "centrally manageable")
(In addition, it should be possible to introduce "Mosaic customizable areas" outside the default content area by introducing new "panels" through portlets or viewlets, but I'm yet to document this feature.)
Once user installs Mosaic add-on, there are no other visible changes than a new "Mosaic layout" view option added for existing content types. (New content types with Layout behavior would have it for default with no other display view options.)
Once user selects "Mosaic layout", a registry configured default layout is used (or error layout is shown when no layout is configured). This layout is centrally managed "static" layout.
Once user clicks edit on content with "Mosaic layout" activated for the first time (or adds a new content with Mosaic layout as itse default view), a layout picker is shown. Picker will show all available layouts for that content type. These layouts are centrally managed "static" layouts.
Once user has selected layout, Mosaic Editor is shows the content with that layout. User can use Mosaic Editor to update content fields (either via inline editable field tiles or through properties menu). Tiles in layout cannot be moved, deleted or added, but layout may include configurable "app tiles" (like content listing tile, RSS tile or even additional rich text tiles), whose configuration can be customized through the editor, while keeping the overall layout centrally managed.
Optionally, user with proper permissions can select to fully "Customize layout". This will copy the selected layout into the content object (to what was previously called "Custom layout"). Now the layout is fully editable.
Optinally, user can "Change layout", which will show the layout picker again. This will abandon customized layout, but may re-use previously customized tile configurations.
This flow is mostly visualized in:
Thanks to @vangheem, who did most of the work to make this flow happen