These patronuses are getting more clever by the minute!!

"Smarter than the averge patronus" indeed!
Interesting of you to extrapolate the Kings Cross 'place' into the Etheric Plane, although in doing so ... are you making the 'land of the dead' - Heaven, Paradise, whatever - just another (pedestrian) world/existence? Oh well, I dare say I'm not supposed to think overly long about it.
And if Hermione knows such much about the Plane, and the ability of a patronus to access same ... I wonder why wizards haven't worked out a way to utilise it for super!apparation purposes? More over-analysing I suspect.
Very nice to bring the Stone into things, as a way to meet the parents, and clever of you to make the spirits' forms corporeal in the Etheric Plane. How did Luna happen to come across it - after Harry tossed it away in the forest - anyway? I think Harry owes Miss Lovegood one super-duper hug for this wedding gift upon his return!
Glad you addressed the Lily/Snape question ... it *was* the elephant in the room, I guess.