A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
A player, 21 February 2008
If I use Arrival of the emerald champion, and someone kills one of my other units, may I hope of death onto emerald champion? If so, does he still disappear at the end of the round?
If I merge with a dishonored personality, does the new merged unit become dishonored?
Title Hope from Death Rarity Rare Edition Text Reaction: After one of your Human Personalities is destroyed during battle, pay his gold cost unless you are a Phoenix Clan player: Overlay his card on one of your target Human Personalities at the current battlefield, ignoring title and experience levels.
Title Rarity Rare Edition Anvil of Despair [ View Printings ] Text Political Battle: If you are the Defender or are attacking a player with a Family Honor below zero, even if you control no units at the current battlefield, discard the Imperial Favor: Create a 5F/6C/3PH Samurai, Duelist Personality in your side there. Remove him from the game after the battle ends.
Zen Faulkes (rules official), 21 February 2008
A player, 22 February 2008
Regarding this topic : viewtopic.php?f=59&t=65833
If I understand the question it was "Can I overlay my dead personality over the Emerald Champion." It looks like your answer was to the question "Can I overlay Emerald Champion onto another personality"
Unless I'm mistaken, you can Hope from Death a dead personality onto the personality card created by Arrival of the Emerald Champion.
Also, according to how it works regarding the Tsuruchi Etsui overlay, the Emerald Champion is at the same time out of play (he leave the game as a created card going out of play as per the overlay rules) but still in play as a fashion (as a basis for upgrading the personality as per the Etsui ruling where Tsuruchi Etsui XP is still considered in play for purpose of his trait when overlayed by it's XP2 version).
As to what happens when the merged Emerald Champion/Dead personality when the battle ends, that's the other part of the question.
Martin Lund (rules official), 27 February 2008
The underlying card’s attachments, tokens, and game state, including ongoing effects, also apply to the new stack, but this does not transfer or attach anything, or begin or end any game state on a card. Specifically, existing bonuses and penalties to the underlying card’s stats will transfer to the overlaying card.
"Remove him from the game after the battle ends." is not an ongoing effect, it is a Delayed Effect that hasn't even been applied yet. I don't see any indication that it will be applied to the new Overlaying card.