The design of this Kamen Rider Gaia was originally of more a traditional Kamen Rider appearance, before later designs switched to a "Kamen Rider Style Reform" version (resembling a man in a motorcycle helmet and modified riding jacket), and then the mutated insect-like human that would become Kamen Rider Shin.
The initial concept for Kamen Rider Gaia was rooted in traditional Kamen Rider aesthetics, but it later branched out into a "Kamen Rider Style Reform" version (resembling a person wearing a motorcycle helmet and modified riding jacket), before eventually morphing into the insect-like human that would become Kamen Rider Shin.