It would be great if you would like to implement this feature and contribute to mojoPortal.
If you are willing to implement all 4 data layers it can be internal and the code can be added to mojoPortal.Web, mojoPortal.Business, and mojoPortal.Data (4 versions).
If you're not sure about implementing all the data layers then I would recommend implement this feature as external projects and when you are finished maybe I will implement any remaining data layers that you don't tackle.
The WebStore.sln has an example of a complex feature implemented as separate projects. The most important trick is using post build events to copy the needed files from the external projects to the correct places beneath the web project. I usually make the UI(web application project) handle the post build copying.
If you have more specific questions as you get into it I'll try to help.