Thank you for sharing your ideas about improving OpenAccess - we appreciate that.
Currently the scenario we recommend for Windows Phone apps is to use OpenAccess on a server and expose your data using Web API or Data Services, as presented in our SDK Browser under the HTML5 / KendoUI section.
While OpenAccess ORM supports SQLite on the server, you cannot use it on the client side of a Windows Phone app due to core framework differences there.
I hope that helps.
the Telerik team
Q3'12 SP1 of OpenAccess ORM packs Multi-Table Entities mapping support. Check it out.