Areas of an axisymmetric model that to not sweep through a full 360 degrees would typically be modeled with plane stress elements. Thickness would be set to represent the portion of the swept volume that actually contains material.
It's unclear from your question whether the elements are to be constant thickness or variable thickness (axisymmetric) based on radius. For true axisymmetry you would want to define a thickness field as a function of radius if you are using plane stress elements, or else construct a 3D "wedge" model. If you're looking at a bladed hub segment, our experience is that the hub is represented as axisymmetric (radially dependent thickness plane stress) and the blade is represented as constant thickness plane stress or a distribution based on its actual thickness.