I’m warming to the idea of the reverse trike, but it has to stay with the leaning vehicle dynamics of the motorcycle to avoid the tendency of the rear wheel of a flat-cornering reverse trike to whip around (ground loop.)
Clearly, the Harley is the most advanced of these (there are others out there). With the driver sitting behind the engine and the passenger in a tandem position (traditional for motorcycles) the next step is to fair this rascal in. The other two are add-on kits. The Harley has the rider sitting low. Harley sells a lot of bikes so people can get on and off them easily and set flat-footed at lights so this is a natural for them. I like the low driver position because that way you can get minimal frontal area without putting the driver into an uncomfortable semi-recumbent position.
By using the motorcycle vehicle dynamics you lean the machine into the curve or wind fairly easily by tilting and letting the change in center of gravity do the work.
Some other thoughts.
Such a machine has to have a reverse gear. The only bike I know of that has a reverse is the Honda Gold Wing.
The “Harley" layout lends itself to having a long-travel sprung seat like 18 wheelers have. Most motorcycles have limited suspension travel and after a day in the saddle your kidneys have had it.
Once faired in, you could add a heater using engine oil or coolant, making the machine a three season motorcycle. Got my doubts about snow or ice. Somebody else can be the test pilot.
The engine/transmission does not have to be from a motorcycle. VW is beginning to market TDIs with six-speed dual clutch transmissions. This solves the reverse problem. You could go front wheel drive, or use a system of timing belts to drive the rear wheel and achieve the optimum gearing.
Accommodating the steering and tilting front wheels will drive the body designer to drink.