There have been a plethora of design concepts on uservoice, here, msdev and neowin forums over the last few years. Some of the best revert somewhat to a combination of the WIn10 and Win8/8.1 desktop models (key point - using groups) in order to make the transition between portrait and landscape more manageable and predictable.
I find myself using landscape mode often now than I did previously (WP user for at least 4 years now) - in the past it was predominantly for Web Browsing, but as other applications have matured on the platform and we see more developers coming onboard I'm using more and more apps more frequently in landscape modes - and switching between apps, start screen and task switcher is very inconsistent.
For instance - why is the task-switcher landscape when the start menu isn't? That seems to defy logic to me as for the designers to accept that sufficient use of the device will require the task-switcher to be 'friendly' in landscape mode they must also apply that same logic to the design of the key centre of the device - i.e. the start menu.
Anyway, this was only meant to be a very short post, as per most discussions here - post feedback in the feedback app (there are many, some very upvoted, threads on landscape mode), that's why it's there. Remember WindowsCentral is a great site for us to all network, discuss, rant, moan and praise the system, but MS don't spend their time here soaking in the comments.