It's a great idea, but you can also make it out of royal icing and combine some small parts with fondant or gum paste. Pipe them out let it dry for 1 day and put it together.

Tutorial bicicletta in pasta di zucchero

Instructions for edible gum paste or marzipan bicycle cake topper, but could be made in polymer clay; photo tutorial, not in English.

bicycle cake

A little classier but still just doesn't feel exciting enough.