<<Metaphysical possibility is determined by a-priori modal intuition, >>
This is meaningless. This isn't a method for determining anything.
Might as well say, "metaphysical possibility is determined by consulting the quartzite metaphysical divining rod".
Metaphysical possibility is determined by determining whether a concept meets the definition of metaphysical possibility.
Which is impossible to do, because metaphysical possibility is poorly defined.
It's not a useful system.
Be that as it may, my point--and, indeed, any point about question begging--revolves around epistemic warrant, and my argument is that the premise <>G demands exactly the same warrant as the question of interest does: G or ~G
The MOA does nothing at all to change the epistemic conditions surrounding the question of interest.
It is literally circular.
It literally begs the question.
In what sense, then, is it worth anything beyond accomplishing what the first four lines of my argument accomplish?
Also, <>(~G) is "possibly, God is not instantiated."