I'm in the process of doing a Sentai, Rider, Cure RP with strong Lovecraftian and Moorcock undertones if you are interested. It isn't quite done yet but ya might have fun participating or reading the story as it unfolds.
The only thing that hasn't really been covered in Ultraman, at least to my limited knowledge, is how the appearence of these massive creatures effects the mental state of the general population. I mean you see even in the original Ultraman series the occasional mad scientist or power hungry bastards (the Jirass episode and magic rock episode) but you don't really see the general public over reacting. Maybe this within itself is a sign of madness with people being so over whelemed by the existance of such creatures, as well as the mass destruction that they can cause, that the population just becomes disillusion. I doubt this was the intent of the series, but it is a fun concept to play with. Perhaps the Ultramen themselves play some part in this by creating a calming, psychic field to help less developed species cope.
It fits very well now that I think about it. Both are massive, semi-cosmic entities who interact with humans in unique ways. Only real difference is Ultramen just have a set of morals that are very much like humanity's. HA! Does this mean Lovecraft was doing Kaijin before Kaijin was a thing?