My thought was a small logo and the SMART name. Could make small kits. Long enough to access the rear tail light feed. Could put inverter and connect in access panel. Figure on 3/4" tall letters and logo.
Certain colors, brightness and location are issues for my state. But I think could get away with it as a 3rd break light in red if wanted, as long as it is above 17" from ground. Other colors like purple, green you can get away with.