Goju has a much more southern kungfu influence as evidenced by the heavy focus on sanchin kata and stance. Their natural evolution would be chi sau, more Wing Chun than taichi, which they have a version of in kakie practice. While Shotokan may never have developed the catalogue of advanced skills and mechanics employed by internal martial artists, I don't see it as too great a leap from the mix of Aikido blending and close quarter striking to develop sticky techniques and close blending drills. Combine this with a bit of exposure to taichi and all the ingredients are there. It may never be push hands but there would be cross over points. And to answer the other question, shotokan is the base of my training. When I reached Brown belt I read an article by the founder of the JKS Harada sensei. They are an offshoot of Egami ryu Shotokai. Harada studied directly under Funakoshi and Egami, but went off on his own eventually. I visited one of the JKS schools for a couple of classes. I don't know how standard they were but they were nothing like the videos; it was just relaxed Shotokan with an emphasis on relaxed power and on blending and unbalancing.