It's a skin I use for 10+ sites and on some sites they want a specific module (e.g. the users personal event calendar) on all pages (except the admin pages).

It just feels as a controversial decision how to handle modules when the pane they are placed in does not exists, no matter which descision is taken.
I wouldn't have been surprised if how to handle orphin modules had been a configuration setting. (And I'm surprised it's not a configuration setting that they should be addedd at the bottom of the content pane instead of at the top.)

I like peter's idea somewhat, although I stronly prefer responsive design instead of separate mobile sites.

I understand. Although I agree with your idea of "certain conditions", you do mention mobile device as an example. I couldn't agree more if the condition were the user's role or location (e.g. the intranet).

I should have spoken about mobile pages instead of mobile sites. We should prevent giving 'mobile user' an other experience as desktop users. This certainly doesn't mean the exact same layout, but it does mean the same (information) content and capabilities. And while we're going off-topic: The whole isMobile detection which DNN does based on a service provided by 51degrees, is flawed. When I connect my smartphone to my full-hd 96" screen, keyboard, mouse and high speed wifi, it is still considered mobile, while my (underpowerd) notebook in the attick with it's 800x600 monitor and  128MB of ram gets served the heavy 'desktop' site. (and I currently have to fake my user agent string as the 51 degrees service reports back that my browser doesn't support javascript, breaking even the most basic of pages as DNN does not work well without javascript. Which makes me wonder (a) how they came to building a login page which depends on javascript, and (b) came to serve that without the javascript if the browser is reported not to support javascript)

I completely believe you have only the best of intentions, but it's very hard to do right when talking about 'mobile'. Even the question "what is a mobile device" is a harder than it might seem.