Create a PBB marketplace
Create a commercial level of PBB that can be sold and provide an online marketplace (ala Apple's App Store) to facilitate it's promotion and sale.
(I suggest that you rename this so that people can find it.)
I agree that the ability to create books and sell them will help attract publishers and see Logos 4 as a serious platform for distributing INTERACTIVE electronic content that is linked with other resources. Of course, there needs to be good copyright protection so that people can't swap them like MP3s.