https://tenchimuyotranslationblog.blogspot.com/2017/03/mihoshi-falls-to-land-of-stars.html
Its interesting that the genesis of Tenchi Muyo was from idea that Kajishima had for a light hearted episode for BGC. Artmic basically recycled and transformed a few of their ideas before as seen here.
https://www.zimmerit.moe/artmic-megazone-design-design-themes-bubblegum-crisis/
Sort of, this is a Hayashi interview after all. I'd say their combined vision of Tenchi came from working together on BGC. Kajishima's designs and core ideas go back to his high school years. Hayashi shaped it, gave the ideas structure and should be commended for it and is rightly given co-creator credit for the series- but the ideas were in Kajishima's head earlier than that. Given that structure, Kajishima finally had a template to further develop his existing story ideas.
Tenchi is what happens when a dream is given shape by an artist. I'd love to see some of these guys get back together to do something interesting. Maybe remake GXP?