A salesman would tell you that people want a tri for different sets of reasons. Some of these are well covered with an HP. Spending saliva on convincing people of these reasons may not be the most productive time spent and in that sense you are right that somebody who wants a tri will get a tri. As Chris pointed out boats on the water with happy customers speak for themselves. The HP is so to say in the doldrums of the chicken and the egg problem: not enough "happy" boats yet stirring the sensitive nerve of more sizable markets (beyond those of this forum) commanding the necessary capital.

Of course we shouldn't turn the HP design into a pretzel just to go after the tri market, but the larger the overlap between the respective capabilities the better. The HP advantages as you argued so well speak for themselves. So the exercise is to see how much some features can be nudged to defend against the most often cited objections. 

My suggestions to your legitimate objections may not hold out to scrutiny but they give the drift of the exercise:

- weight "aft": provide an option to install tubing for holding canvas stools at the bow ends; install folding horizontal foil on dedicated "aft" end.

- lack of rocker: provide the option to exaggerate some the angle of the bottom plane; optional central board (just for tacking around); optional bow thruster ...

As these are options they would not detract from the "pure" HP experience.