Simple really.
If Ironmans a.i. achieves the astral plane he can advance in that form in his own mind further negating the narcissism he has been battling.
Bringing another along there to battle would be as easy as developing the War Machine armor for Ironman.
Therefor Iceman's power whos only limit is his own conscious could war on the astral plane in this fight of the mind.
To simplify. Ironman and Icemans consciousness on the astral plane. Who wins?