Because right from the start your list player’s unit doesn’t have this character, If you want to join enemy with your allies, you need to set one character in your list player to be like enemy.
But in FE8 available, You can let any enemy join allies without lose any character from allies but in TRS Unavailable ?
I don’t like lose any characters, I’m sure if I find offset in file iso/bin will be allies because not everything must change in quick save state in some games, by the method I can add any enemies
You can do it in TRS, it’s unavailable.
I will try, who know if available or unavailable ?