Thanks for sharing this with the rest of the community. Hopefully, the community will provide you more feedback.
I have read some parts of the documentation in the home page of your project, so I would like to give you my personal appreciations. It is clear you were pretty inspired in Prism and others. So, this is just great, since Prism is meant to be a guidance.
As for the Validation, in Prism 4 the ViewModel base class supports setting validation errors for the properties of the view model or model. Therefore, you will find guidance on this topic in the MVVM Quickstart and in the following documentation section
in the Prism4.chm: MVVM Quickstart, see the Validation section.
In terms of providing you a more MEFEE code, in the Stock Trader RI, you will find a new ViewExport attribute, which helps you on exporting this to the container as well as register this in a particular region.
[ViewExport(RegionName = "MainRegion")]
You could check the Stock Trader RI if you need more guidance on this topic.
It is pretty interesting the concept of Areas, which is similar to Regions and the way that it is managed without Region Adapters by creating interfaces. In my personal opinion it is a simpler approach in cases that you need to expose new controls for which
you do not to add a Region Adapter, but in most cases it could comprises the productivity. Additionally, it loses the ability of UI Composition in an homogenized way between different applications, you need to write for each view.
It seems that you worked hard on this and also provided a lot of guidance. Personally, I found this really valuable, so I would encourage you to continue on this project.
Just for you to take it into account, you could use
Codeplex as another option to manage your own open source projects.
Hope this helps.