Delirium says:
... only using it as an example for a core feature from another playbook that would require some heavy narrative justification. ...
Understood. I used it thusly too. :)
As you say, it would require a heavy justification in the narrative, and that vampire core Move makes you some sort of monster that feeds off others to stay alive, it is not just the healing, it is also the driving Hunger, so you are not exactly human anymore. Not sure how this would be different to being a vampire, but it could make you a vampire with Relationships? You would be a vampire using the Aware playbook, it may not hold and you may end up slipping into full vampire over time, losing those relationships and gaining corruption... but this is all narrative, in-fiction stuff, and not addressed by the mechanics.
You can (hypothetically) do it, it will cost you.
Delirium says:
... 'More Lives to Live' is basically the core Immortal's Move, for coming back from the dead. ...
That looks pretty easy to take, but, as with
Persephone's experience, dying and coming back will change you, I am not sure how long you could reasonably stay The Aware once that starts happening, so it may be more reasonable to change to that Playbook, or need to do so at some point? Maybe only a century from now, but the game's timeframe will dictate how much it affects you, how often you die and come back will also affect you. Mechanically the Move changes you, too.
By the rules you are allowed to take those core Moves, they are 'Moves in another Playbook'.
Taking a Move from a Playbook in play comes with a conversation with the player playing them.
Taking a Move from Playbook that is not in the book comes with a conversation about whether that playbooks is part of the game. Assume they are not unless the GM says they are.
The GM might also 'limit the field', only allowing certain Playbooks. This is common practice when the GM wants to shape the game. We ended up with soft restrictions on The Fae and The Wolf, but only because they got entwined in the story due to initial player choices.