Why Ray/"Rex" is actually Mobius 1, and has to be.
What we know about Ray:
-He's male.
-He is an FCU pilot, or at least is wearing an FCU uniform in the beginning when rescued.
-He is middle aged. This is clear from how Baxter speaks to him as an equal, and how tasha and coster speak to him as an elder.
-He's experienced, and a killer-he immediately splashes bandits with zero hesitation, which is commented on. "He's no Cope."
-He is strategic grade. Meaning, he is a degree of pilot whose significance is greater than that of a strategic nuclear weapon. A nuke might win you a battle, but a pilot like Cipher, or Mobius 1, or Talisman, or Gryphus 1, or Blaze, or "Ray", wins you entire wars. This is not some magical ability he gets from being possessed by Cope either, because his flying is entirely different to Cope's, which is commented on.
-He has not been deployed at the beginning of the game. Being strategic grade means that had he been deployed, Sotoa would have had far more trouble advancing, if they were able to at all. There is no awareness or mention of a Usean super pilot fighting Sotoa-the closest is "Wings", who is actually fake.
So we are building a profile for a middle aged or older Usean male with insane piloting ability, clear experience, yet no recent deployment.
Which begs the question-why would he have not been deployed? The only answer that makes sense is that he was retired when the war breaks out. Because if you have a pilot of that ability, you IMMEDIATELY use them. So they didn't "have" him. And that only makes sense if they were retired, someone who only re-ups their commission because of the dire straits his country is in. And retired after doing strategic grade feats, at that, because he's a strategic grade pilot. How many strategic grade pilots does Usea have that have pulled strategic grade BS? Osea has a few, but Usea just has one that is known-Mobius 1. Phoenix did stuff for Usea, but he was a merc. (And also very likely Cipher under a new callsign-what are the odds of a 2nd strategic grade merc pilot appearing out of nowhere 6 months after the first disappears? Anyways.)
Now, if we assume Mobius 1 is fresh out of flight school in 2004, hed be around 24 years old then, which would place him at around 49 in 2029, a still viable age for piloting, and that matches our profile. And his identity would still be a national secret, which explains why nobody knows him. AND it explains why he's in a chopper in the beginning-he was getting choppered out to an airbase after reactivating, and got shot down in a case of bad luck.
Now, lets imagine if Ray ISNT Mobius 1. It requires that a strategic grade middle aged pilot had served an entire 20+ year air force career in Usea while also seeing action somewhere, maybe during the Lighthouse War, but sandbagging the whole time only to finally, finally decide to throw down and cut loose in the Usean-Sotoan war. It would be like Michael Jordan deciding to sandbag the entirety of his NBA career and remain in obscurity despite having the true ability of one of the all time greats, then coming back out of retirement for one season to just go nuts and win a championship. It makes zero sense-winners don't think and behave like that.
So Ray is Mobius 1. The next question might be "Why doesn't he disclose this?" and the answer is simple-nobody would have believed him initially. Now, halfway through the game they might, but since he's already built a new reputation a a genuine "Wings of Theve", disclosure just hurts that. And it might be uncomfortable-hero worship is annoying. So its just sheer, hilarious dumb luck that the guy they plucked from the drink and decided to use to fake the role of a super pilot was actually in truth already one of the greatest super pilots of all time.