I get them on my European game without custom dlc.
What I did was, download them on my ファイアーエムブレムif version and saved the game.
Then I dumped the extdata with SaveDataFiler.
Then I dumped my extdata from my European limited edition .
Delete every file in my European extdata and copy my japanese data in it.
Then I restored this extdata with JKSM in my European version.
Of course, I copied the units with Feftwiddler from my Japanese save, to my European save.
Everything works perfectly expect their names appears as ???, which is normal since hiragana doesn't exist in our ASCII table.
No custom dlc are needed, I just using my data from my Japanese game.