This design was inspired by the big guy himself, although in the fan story this guy comes from, this one with the "H" is nicknamed Hyper MechaGodzilla, because the first Super MechaGodzilla, or SMG-Ist, was smaller and had less battery power.
Taking inspo from MonsterVerse, SMG-IInd has the skull of Ghidorah, or more specifically the benevolent Thousand-Year Dragon King Ghidorah. And like in the anime continuity, SMG-IInd uses nanometal as a weapon, but nanometal in this continuity is more of a repair/reinforcement material than a direct weapon.