Hi Tim,
It is very common to factor out common shared code into a class library that gets reused across modules and the shell within the same app or across apps. The main consideration would be whether that shared functionality can be constrained to only being used within a WPF or full .NET framework app, or whether it also needs to be portable to other XAML platforms like WinRT or Windows Phone or Xamarin. The latter constrains you a lot more. I'd recommend you check out our new version that is in work at http://github.com/prismlibrary/ - we have refactored as much as possible into a single PCL for the Prism.Core stuff and then have platform specific variants for the other XAML platforms.
Bottom line as long as the shared functionality is going to be used only in WPF or full .NET framework apps, you should have no problem.
It is very common to factor out common shared code into a class library that gets reused across modules and the shell within the same app or across apps. The main consideration would be whether that shared functionality can be constrained to only being used within a WPF or full .NET framework app, or whether it also needs to be portable to other XAML platforms like WinRT or Windows Phone or Xamarin. The latter constrains you a lot more. I'd recommend you check out our new version that is in work at http://github.com/prismlibrary/ - we have refactored as much as possible into a single PCL for the Prism.Core stuff and then have platform specific variants for the other XAML platforms.
Bottom line as long as the shared functionality is going to be used only in WPF or full .NET framework apps, you should have no problem.