Perhaps a workflow similar to this one would work - automate the creation of a legend view for each rebar shape, export each legend view as an image, load the images and set the rebar’s parameter values, then remove the legends:
EDIT: Apologies, I hadn’t realized rebar shapes could not function as legend components. I’d imagine, however, you could do something where you automate the creation of an isolated axonometric view for one instance of each rebar shape and export that view as an image