They went back and forth like this a bit before settling on the final design, and Toriyama was insistent on the form not being too different from Goku's regular appearance, specifically not being really muscular.
The series' original author, Akira Toriyama, came up with a picture of Super Saiyan God that was completely different than Yamamuro's own initial muscular, cloaked design. According to interviews with the Battle of Gods character designer, Tadayoshi Yamamuro, the original concept for Super Saiyan God, had the form being more muscular, wearing a cape, and with a hairstyle in-between Super Saiyan 3 and Super Saiyan 4.
