Interesting the light arrangement at the rear, with only the two units above the numberplate being brake lights. Also the overall light positions and types. Certainly bears looking at closely as it appears it would not be too hard to use the units on a vintage twin. In case anyone wonders, no vintage trike should be original in this respect now as the law on rear lighting changed in the 1950s and is one of the few motoring laws to be retrospective. Many now use lights from a Triumph Mayflower but the modern units look as though they may present an acceptable alternative.
Here's a photo with all lights showing Martyn, number two s-i-l (my passenger) has even obligingly turned on the rear fog light:
Doesn't the trike look tiny compared with that Volvo XC90?

Hope that helps with your decision making process
As regards strictly non-legal number plates, I've driven the Aero SS with black number plates for some 18-months and have only just had legal ones fitted. During that time I have only had a verbal warning once by a BiB who came over to look at the car in a petrol station and knew exactly what model it was as he was a PH aficionado.