Today navigation properties must be direct children of the entity. We should support navigation properties being defined on properties grouped into a complex type. For example:
<ComplexType Name="Address">
<Property Name="Street" Type="Edm.String" />
<NavigationProperty Name="City" Type="MyModel.City" />
<NavigationProperty Name="Region" Type="MyModel.Region" />
<NavigationProperty Name="Country" Type="MyModel.Country" />
</ComplexType>
If a type <Person> has an Address, then you could express the navigation property binding as:
<EntitySet Name="People" Type="Person">
<NavigationPropertyBinding Path="Address/City" EntitySet="Cities"/>
<NavigationPropertyBinding Path="Address/Region" EntitySet="Regions"/>
<NavigationPropertyBinding Path="Address/Country" EntitySet="Countries"/>
</EntitySet>