This article is from the Anime FAQ, by Steve Pearl with numerous contributions by others.
Sonoda Kenichi did not create Bubblegum Crisis. He worked on character and mechanical designs for the first four episodes, and assisted on production designs on the last episode. The reason he is credited with character designs on episodes 5-8 is that character designs he did for episodes 1-4 were reused. Gooda Hiroaki and Urushibara Satoshi designed all the new characters in episodes 5-8. Sonoda is also credited with the character designs in Bubblegum Crash for the same reason, i.e., old character designs of his were recycled. Also, Sonoda was second choice for this job; he was tapped only after Artmic's first choice, Amano Yoshitaka (known for his character designs on such features as Gatchaman, Mospeada, Vampire Hunter D and Tenshi no Tamago), turned it down because he didn't want to do mechanical designs. The series was created by Suzuki Toshimichi, founder and president of Artmic, and author of the screenplays for episodes 5-7.
Addendum: Sonoda started out working on Moonlight Rambler, but quit partway through, for reasons not entirely clear. Gooda Hiroaki took over at that point; Largo is his original design, for example. Sonoda also did the cover art for the videocassette and LD editions of all eight episodes of Crisis, all the Crisis CDs, and both Hurricane Live videos, which may explain his involvement in the character design process of later episodes.
As for Vision, he did all the cover art for Double Vision (see above). Also, Urushibara intended the Vision design to be based on an older version of Irene, so Sonoda's work was at least tangentially involved here too.
-Michael House (AnimEigo)