Themes are not UI updates. The Today Plus "theme" is a UI completely unique from anything else. You can reicon, recolour, rebrand the interface in many ways, but you still have the same interface you started with. To date only Icon and list themes on 4.1 devices can be made/moidfied, and dimension zen and list on 8100. Anything else like phantom, today plus, zen for 8700, etc, which have different UIs, were made by RIM.
Perhaps YOU should do some looking!