Despite the length of this post, the outcome I've tried to achieve is really very simple.
Quick précis: I run a series of publishing titles (magazines and websites) and receive dozens of enquiries from would-be writers who'd like to see their work presented in our unique style. We've run several award-winning social communities and decided to revamp our automotive site to provide more of a showcase for aspiring writers and bloggers. We've built many wordpress sites and finally decided to give BuddyPress a chance to fulfil our needs.
Proposed Architecture:WordPress multisite using BP Default as a base theme but with a heavily modified design, the same theme is used for all the user sites. These user sites are configured to operate like pages of the main site. SWT plugin is used to aggregate all posts (from the main site and user sites) onto the homepage of the main site - just like wordpress.com
Publishing: The blog posts are all of a Tumblog format (Tumblr like) - they are created using an interface where the user chooses between video, link, quote, audio, image or asides.
When a post is published from any site within the network, the tags blog is updated and the main site shows the aggregated listing of these posts. That all works fine.
What I am trying to do (very simply) is to update the tags blog with the same metadata (custom fields) that are saved on the user blog posting, so that this index of posts can also reflect the tumblr style of each post. There are conditional statements which check the type of post format and then display a specific icon, default image etc.
What's the problem?: As mentioned previously, the post metadata is not being included in the main tags blog, therefore the tumblr formatting is lost when viewed on the main site. Don't get sidetracked by the BuddyPress context, unless of course its relevant to the WP functionality available.
BP works fine, each new post is reflected in the activity stream - I'm not bothered identifying the post formats at an activity stream level.
I'm well aware of the differences between post types, post formats, and custom taxonomies. Initially I tried to use custom taxonomies, but changed to post formats because these are how future versions of WP will be developed.
What code am I using: At this very moment, I'm only using the SWT plugin code configured with the custom fields used as the meta_keys of the post formats in use - video-embed, link-url, quote-copy, quote-author, quote-url, audio, image.
After trying various routes including the SWT filters (which didn't work) and even considering a direct database query to bypass the WP functions, I decided to try and make the in-built plugin function work.
You can view the code for yourself in sitewide-tags.php from Donncha and Ron's plugin.
Visual representation: I can't share the URL with you, the site is hidden behind a redirect whilst I fix this problem, but here's a screengrab to show how the front-end looks.