Well, it was this statement that gave me that impression:
"The first package containing the datamodel, tcl api and reusable includes in package-key/lib."
I guess if you'd said "with resuable includes placed in package-key/lib" or something like that I would've understood your meaning ...
So far my major concern is the note that using ad_conn would be impossible. In the include chunks, yes, and this is true of portlet code as well. But I would imagine the UI packages themselves would be normally mounted and would have package_id available. There are issues involving URL generation from the functionality package ... if it's not mounted how can it call pages within itself? It might be possible to drive the UI package with an index.vuh file that can resolve links into the functionality package by doing includes or something like that, haven't really thought it out.
You may be interested to hear that my original thinking for the portals package, and something I urged Open Force to consider, was to make portlets renderable in a stand-alone fashion rather than only via calls from the portals package.
You can actually do that with some work by dummying up the right array values to pass into the portlet but it's not necessarily straightforward.
If we are going to adopt a TIP along these lines I'd like us to look into being able to share as many UI chunks as possible between portlets and standalone pages. In .LRN some refactoring was done in packages to do some sharing but it's all ad hoc.
