well, even so, most of us will have to use patched and moded system files because nokia will not do anything more there...though...
anyhow, if you are able to replace /usr/share/themes/base/meegotouch/sysuid/style/statusarea.css by regular installation (similar to meegotouchhome) then it would be possible to write some code that will make landscape and portrait backgrounds. i am not really linux master, but i think it can be done, though?