A being cannot exist by nature because nature presupposes existence. To exist by nature would mean that nature “causes” existence, but it is not possible because for nature to be operative, it has first to exist. A nature must exist, and then can “cause” something. It is a matter of ontological priority.
Therefore, I don’t see any intelligible meaning in the statement that God exists by nature.
thats all well and good (currently no ontological argument does hold water).
However, some things do appear to exist by their nature:
The existential statement: “There are two prime numbers between 10 and 15” is true because of the nature of prime numbers. That is to say, the concept “prime numbers between 10 and 15” implies existence by its nature.
Given this, i wouldnt rule out more exciting ontological arguments in the future which are slightly harder to smack down than the traditional ones.
I see that you have read “The non-existence of God”. 
yup, but i dont really agree with that conclusion, I’m just interested in what your reply is.
Its a shame Everitt didnt have a looky at combining this argument with the Frege stuff just before it:
It seems that as existential statements are about number, there seems to be no problem in the natures of numbers (and ONLY numbers) having existential import. This keeps it intact as a general principle to defuse ontological arguments. I don’t know a great deal else about Frege’s work, so I dunno if this would work but it feels right.