Though it seems if we accept List<javax.faces.model.SelectItem> as a model, we should accept child f:selectItems as a model, upon deeper inspection, the component tree is a very ill suited place to keep the model for the list.
f:selectItem isn't mutable, so these would only be worthwhile in lists where you never want to reorder or migrate your items. Not worth persuing.
f:selectItems may be mutable, despite not being indented for that use. But then f:selectItems is essentially acting as extra markup to define what you could've defined as part of the value property of the list itself. Redundant.