Show parents of entry in custom entries field extending BaseRelationField

The default BaseRelationField shows only the name of the selected entry in the field (e.g. "SubEntryX"). I created a custom entries field by extending the BaseRelationField in a module. Now what would be an elegant way to also show the parent of an entry in the field (e.g. "ParentEntryX > SubEntryX".

I think this would be possible by using a custom template for the field using protected $inputTemplate = 'customtemplate'; but it seems like an overkill.