I'm not sure what you mean by "stand alone". Everything I'm working on runs on top of mojoPortal, whether they could be made to run outside mojoPortal is not something I will put any energy into.
The Newletter feature will be a core feature of the site and implemented in the main projects. The e-commerce feature is implemented as external projects in Visual Studio but integrates in the site as a content system feature (i.e. it can be put on a content page). The Newsletter feature administration is not a feature that will plug into content pages, it is a per site feature. A site can have more than 1 store since WebStore is a content system feature. Users of the e-commerce feature will of course be able to use the Newsletter feature as a marketing tool for the Webstore.
I may implement some features of Newsletter in SiteOffice but at first it will not be. I'm still going through some protoyping of the SiteOffice plugin model and am currently re-doing the site office layout using ExtJs instead of dojo and open rico.
Joe