I need to think about this proposal a bit before responding, but one question I have ... what is the benefit of moving datamodel and tcl API code from their traditional directories in the forums-core package?
If everything other than the /www/* default UI lives under /lib then ... why have /lib? :) Why not just /tcl and /sql as we do now reserving /lib for reusable includable templates as we also do now?
I'm not seeing the need for this part of the TIP, which would require APM modifications to support and which would leave some packages using the old style and others the new style directory structure, confusing newbies and probably old farts like me alike.
Splitting of functionality and UI is useful and as mentioned above has been partially done in .LRN though not with the notion of providing multiple UIs to a single functional package base.
You might study some of the .LRN portlet/package pairs if you've not done so already to see how this is done. It doesn't solve your problem but might be source of more ideas.
