I have no idea how Achillie's immortality could face up. It is part of the time before the Age of Man, so it would be targeted. And he, unlike that, has a legitiment and exploitable weakness-- his heel. Even more so, since he is Lancer, not Rider.
Well in a situation like this, it becomes a battle of concepts.
Like for example, lets say I really want to ruin everyones day and apply Berserker!Herc
Pellinore uses Questing Beast and said Beast tries to slash Herc.
God hand blocks any attack that is at or below B rank, no questions asked. Could be a world buster attack and if it's B rank Herc walks it off.
However, Questing Beast is anti-AoG and anti-Divine curse, which is what god hand is. But, Questing Beasts attack is unranked, thus it shouldn't do anything to Herc.
If it's like that, it becomes a battle of concepts between the concept of God Hand and Questing Beasts "End AoG"