I don't think there are absolute features of a good implant design. It all depends on someone's face. An implant on someone with a big skull might look good on him but might look terrible on someone with a small face. Also, designs are 2d. You deal with a 3d face. The key factor is 'seeing' how a 2d design will translate in 3d. It's art, you need to 'see' t, feel it, just like Bob Ross translated the image in his mind into a realistic painting. Most people aren't able to draw a landscape. The artist could explain it technically, but still most people won't be able to get on the same level.
I agree, you must never forget that each implant design is a work of art to enhance a specific individual's face. What I like about this implant is that it addressed the problems with this guy's lower third without overdoing it, assuming that the swelling will come down further. The obvious need for flatter manibular plane angles probably made the implant design process quite straight forward and not too difficult it seems. At the same time, this design on my face would have been a disaster.
But I also believe that there must be some commonalities in all implant design that tries to achieve the same goal. Of particular interest to me is the width of the jaw implant in relation to the bizygomatic width. If the goal is a more masculine appearance without overdoing it, is there a sweet spot?