When Vic first started writing about the BMW design of shock absorber I plotted a.graph on here of the way that design moves in and out with rotation of the two main parts. If the restorative force is being applied by a spring(s) used over its linear range then the shape of that graph also illustrates the way in which the force changes. I am away from home at the moment so cannot bring up that graph just now. My memory is that the shapes of the two parts of the cams means that the force rises more rapidly than linearly. Without access to the bits I need I cannot be sure, but I think that the Vincent design is intended to produce a linearly increasing force. Now why would one be better than the other?
I have written before that John Emmanuel, using a stroboscope, found that the standard Vincent design went easily from a peak to peak configuration depending upon whether the system was in drive or over running mode. Not enough spring force? I have also written about Dick Sherwins experience with flitting the stronger Australian ESA to his oversized twin and sidecar. With this he found that there was almost no movement of one part of the cam and the other as witnessed by the wear marks on the cam faces. Removing a few of the springs solved that problem.
So that now brings us back to the question of whether one wants a linear increase of spring pressure or an "exponential" one. Given decent design criteria, and accurate machining, then I cannot see why the linear system should not work. On the other hand if the forces applied are likely to be outside the design criteria then the BMW system will be more forgiving
Regarding 3D drawings then, I produce a lot of these although I am self taught and use a nineteen year old version of ACAD, it's what I can afford you know. The question with a lot of similar projects is how many will sell? I have sold about 150 of the JE steering heads over the last few years. This despite that it is a major improvement to comfort and safety and is generally not noticeable when looking at the bike. Producing 3D drawings of a hybrid ESA would not be a major task but, for example, with my background as an astronomer I would require advice as to the correct tooth form to mesh with a chain.