Do you think Gabe and Raphael (and maybe lower ranking angels too) have True Vessels? Or was it just a one-time apology gift thing for Luci and Michael from God, for all the shit he's done to them?
I’m not sure that I’d call it a “gift,” but I do think it’s unique to Luci and Mikey. Every angel has a “bloodline,” I believe, or certain people who are more compatible with their Grace, but none of them seem to burn through their vessels as Lucifer did, regardless of how long they possess them.
That probably has something to do with Michael and Lucifer being the two most powerful Archangels in creation, as well as their “destiny” playing into God’s penchant for overreacting (and just being dramatic, in general). It all stems from the “As it is Above, so, too, shall it be Below,” ideal, with Sam and Dean’s paths paralleling those of Lucifer’s and Michael’s so closely.
It also seems to suggest that God did, in fact, keep some control over his supposed plan, as, with two True Vessels being preordained, the sequence and timeframe of events were far easier to pinpoint, given that Sam and Dean would need to be alive, and their relationship in a certain state before anything more became possible.
“Whatever choices you make, whatever details you alter, we will always end up here.” If we consider how certain both Michael and Lucifer seemed to be about how things would end, it seems that little was left to chance. I’d even venture so far as to say that Michael’s indifference toward Dean was, in part, due to the knowledge that he had another option at his disposal.
As for the gift thing... I think, in Lucifer’s mind, Sam being his True Vessel was a gift. It was one of the few things his Father promised him in the way of hope - the one light at the end of the dark tunnel he had been cast into. For Lucifer, Sam was a chance to finally have someone who understood him and understood that he was constantly struggling with his own heart, and that he was not just a monster bred of hatred. But, as we’ve seen, that hope he put into Sam backfired on him horrifically, if only because Sam didn’t have the promise of being rewarded for his patience. To Lucifer, Sam was a God meant to save him, and for Sam, God was a man who told him no one else would care if he was saved.
So, yes, in sentimental ways, having a True Vessel had been a gift. Logically, however, it was just another way to bind the Archangels - to contain their power at a certain time and place, so that they might have a chance at being controlled and predicted. It also served as a way to reiterate the importance of Free Will (something Lucifer has always treated with reverence), making consent absolutely essential, and putting into check and, perhaps, even humbling two powerful creatures who were accustomed to simply taking what they wanted.
Maybe God had hoped that, with these intimate connections to two humans, his sons would learn to appreciate humankind - to see them as something more than just careless, mindless monkeys, and I think it could have worked, if only Sam and Dean had considered attempting to reason, rather than to fight (not that Michael probably would have listened to much reason...). In the end, none of it seemed to make a difference, and it’s hard to say what God really had in mind, if anything, at all.
{{I’d say we might learn more in S13 with the AU world... but let’s face it - post S5 is irrelevant to the true Archangels, so far as Kripke’s work is concerned.)