I think the problem with a roof like this would be wind. Traditional (cedar shake or slate or clay tile) shingle roofs are rigid, so the wind can’t lift the edge. Asphalt shingles are floppy, but have an adhesive strip that glues the bottom edges down to the layer below once they’ve been installed and warmed up by the sun for a while. These license plates are likely not glued down and would be relatively easy for the wind to bend or rip the fasteners out of, so I think durability in high winds would be sub-standard.