I'm not an experienced breeder, the total opposite actually. But freeways are on market now for around 1000 dollars your side (states). How much would a proven 100% asphalt cost? Then the YB and the rats/ energy to get them to size to grow? Its probably more time/ cost effective just to purchase one.
I'd imagine it would be far less fun and exciting though.
I love the thought of a pastel freeway DG.