Cutting these panels on a CNC router is the easy part. Finding the appropriate pattern is the real challenge.  These will someday be the front panels of a series of custom radiator covers, so thinking about the way hot air will pass through is a must. Also, the tolerance of the 1/2″ plywood will be tricky if the slots get too long and thin, like in the second option. Although thinner is better aesthetically, it may make the panel too fragile to be realistic. Although none of these feel right just yet, you have to start exploring geometry somewhere.