The way it is structured now I only seem to be able to access gml:AbstractFeature via the ServiceAreaType (datatype extends EmixInterfaceType)
I noticed that serviceArea is part of the emixInterface substitution group. That group has ServiceDeliveryPoint, PNode, and other locations applicable to a price.
It seems that we should use the same structure to define and extend a price location as used for event and resource locations.i.e probably make the ApplicableLocation part of the same substitution group as ServiceDeliveryPoint, Pnode, etc. And include ServiceArea (or whatever it takes to pull in the gml stuff) as part of that.