Honestly its not too hard to find old Kenner/Hasbro people on linked-in/instagram/facebook. My recommendation is that you try sending messages there. Kenner/Hasbro isn't that big a company in the design departments all things considered, its likely that if it was done in house it was done by somebody who knows somebody on a design team.
Its actually amazing how apathetic the fandom can be when it comes to looking this up. I've see anonymous people on /co/ and /toy/ do more work into finding info on this than longterm fans.
Like for example, M Sipher in the Transformers fandom claimed that Machine wars was made after botcon because of fan response to a Kenner employee's claim they were gonna make a G1 line. He claimed the Kenner employee who said it was actually making things up and disappeared after that Botcon...but that's not true at all, I was able to look up videos from that Botcon, found the employee, and am trying to reach out to him to see if I can ask some questions.