Portrait Mode should have its own 4 panormaic Portrait Desktops independent of the 4 panoramic Landscape Desktops (ie device has 8 desktops in total).
This is an alternative Solution to Solution #1 and Solution #6
The 4 x Portrait and 4 x Landscape desktops would be totally independent.
Switching device from Landscape to Portrait orientation would not involve "rotating" the Landscape desktop, but rather, switching to a completely separate Portrait desktop.
Device remembers last Desktop shown for a particular Orientation and switches to that Desktop when the Device next switches to that Orientation.
User will start with clean Portrait Desktops (just as they start with clean Landscape Desktops). User can add widgets, shortcuts, contacts, bookmarks etc to each of the four Portrait Desktops as they wish. Configuring the Portrait Desktops will be completely independent of the configuring of the Landscape Desktops. The user will be responsible for setting up all 8 desktops (4 landscape and 4 portrait) as they wish.
Portrait Wallpapers will be 480(w) x 800(h) [or if continuous across all 4 panoramic Portrait desktops, then 1920(w) x 800(h)].
Switching between the 4 panoramic Portrait Desktops will still involve swiping left or right.
On the Portrait Desktop, Status Bar will still be across the top of the (portrait orientated) screen with Dashboard/Apps button in top left corner of Status Bar.
In Portrait Mode, Dashboard would show same App thumbnails as the Landscape Dashboard, but instead of being up to 3 rows high x 4 icons across, it would be up to 5 rows high x 2 icons across. Again, with button in top left corner of portrait orientated screen.
Similarly, Apps Menu in Portrait mode would be 5 rows x 3 icons across, rather than 3 rows x 5 icons as in Landscape.