Since we are now being introduced to Rodan, Hollywood style, I would have hoped, that they had cast George Takei, as perhaps a "Rodan expert."
And with Ghidrah, perhaps they could have considered in a small role (astronaut perhaps?), Jeb Stuart Adams, Nick's son, but apparently, he is now retired from acting, and has become a realtor.
And this slime bit
can be an interesting arc. We shall see how they handle this.