Okay, I lied. One last set of Warframe 1999 spoiler thoughts to get them out of my system:
Bookending the story with Transference into Arthur (once very rudely without permission to start off on the wrong foot, once begrudgingly with permission to bring them home) is just great theming structure. Building thematic parallels into your story isn't hard, it's just so much better when the characters' and their growth reinforce their meaning.
On the surface, the Drifter's "help" to the Hex looks like a mere cheerleading pep talk, but that's not how I took it. Who knows more about fully matured Warframe powers than the Tenno? How can they lend that expertise to the Hex in their desperate moments? Eleanor can wrangle the Infestation within with a little willpower boost; Tenno do it all the time, or else their Warframes would be out of control. "Quincy, remember, your frame has the Seek power and it's busted." Aoi especially just needed a bit of support from someone who's used a fully kitted-out Mag before and mastered her magnetic powers. "Amir, here's something you would have never found out on your own: Your Warframe body has a Parazon, which doubles as a hidden blade AND a data-link!" And, of course, Arthur - if your body can't move, then I can move it for you. It's all the Tenno being an experienced Tenno to help the Hex.
I was definitely in the camp of "wait, I thought Albrecht shot Amir- OH THANK GOODNESS WE STOPPED THAT."
It's so incredibly great that the instant-messenger stuff allows us to discuss and digest a lot of Warframe's weirder lore in an in-character way, on top of all the other ways it's great. Love me a game system that accomplishes multiple goals at once for different player interests.
My absolute favorite thing overall? Thematically, this is a mirror-image of The Sacrifice. Somehow, through sheer empathy if nothing else, the Tenno have the power to share their inner strength with troubled, broken, hopeless beings, take away their pain, and unlock their full potential. The Operator did it with Umbra (and by extension every other fully converted Warframe), and now the Drifter's done something arguably even more impressive - using that power on partially still-living humans, with understanding, consent, and mercy.
Look, I'm arguably a writer by trade. I love analyzing story structure, and I especially love seeing action genres take a stab at being emotional, vulnerable, and empathetic while still being kickass action. That's a delicate balance, but oh boy does it make for a delicious dish for my particular palette.