But since averaging tracks used also for rotation cannot in my experience make the track worse, only better, it's something I'd like to see implemented.
I'd say go ahead and implement it in your version of TrackerViz, then. TrackerViz was kind of born out of my wanting a way to visually see every track I was going to use before I used it. I very, very much like the ability to average together a ton of tracks, and then lock that new averaged one as the Position. Then I do the same thing for where I want the Rotation to be calculated from. I like being able to totally nail down the position separately from the rotation.
For example, say I have some handheld footage of a computer desk with no computer mouse. I want to put in the computer mouse. I would track the spot where I want the mouse to sit maybe 8 times, then average them all together. That's my position. Then I would track the spot where the mouse cable goes out of view under the monitor stand. I would again track it 8 times and average it together. When I use TrackerViz to calculate the Pos Scl Rot, it locks it down where the position one is and calculates Scl and Rot from the other point. If it calculated that second point into the first, the mouse would NOT be locked down to the spot I wanted it to be. It would be moving in the same path as a point halfway between the 2 points I used, which would be incorrect movement. Hope that makes sense.