Library - Plugin Architecture
This would be one of the best solutions (and quickest possibly to implement) for allowing the Entourage to read ebooks in other formats, without having to release full documentation/developer tools to use the e-ink screen.
There are a number of various e-book/document formats out there, and instead of forcing developers to write out a full UI and functionality of a third party e-book reader app, why doesn't Entourage update the Library app so it can accept plug-ins for other formats. This would keep the UI stable so it's easier to use, and it would be quicker to develop a functional plug-in for most third party formats (djvu, chm, docx, and others).
This type of functionality would give the eDGe a huge boost over the competition, allowing the eDGe to be relatively independent of imposed supported formats.