A cool feature I thought of, is to be able to put images on your rocket, this would open up many opportunities for modding in textures. Another idea I had was to let the user decide how many edges, vertices and sides they want on their part, therefore allowing you to make squares and triangles and more detailed and complicated shapes.
I already made this suggestion. https://www.simplerockets.com/Feedback/View/2XGg49/Text-Label-part-that-you-can-use-to-add-text-to-your-rocket