My scenario: trying to port a small part of an application created by our company from native code (ObjC for iOS / Java for Android) to C-Sharp. The project will interact with o
Perhaps you want to look at the efforts other who have got PCLs working to a considerable degree with monotouch and monodroid.
For example see http://www.slideshare.net/cirrious/mvvm-cross-going-portable . You'll also find instructions on how to setup PCL support for MVVMCross here http://slodge.blogspot.co.uk/2012/09/mvvmcross-vnext-portable-class.html .
Xamarin has recently committed to providing far greater PCL support rather than some of the workarounds that people have been having to make, but it is worth the effort.