Honestly, Mirage reads very much as Jazz. Not sure why they didn't go with him, tbh. But yeah, this Mirage seems very.. idk. In G1 (or at least popular fanon, I've only watched the first two seasons and that was years ago) he's a bit more emotionally distant. I think he was a noble back on Cybertron? He seems more open in the trailers.
That's exactly what I thought as soon as I heard him speak. I wondered why they didn't just make him Jazz, because that voice line, the way he fist-bumped the human, it definitely carried casual, confident attitude that screamed 'Jazz' all over it. I had this suspicion ever since I saw his alt mode, but now I'm 100% sure he was supposed to be Jazz but had his nametag switched around for some reason. They've already pulled the same bullscrap on Blitzwing in Bumblebee movie, if I remember correctly.
Although I kind of understand why they didn't choose Jazz, because he is closer to 'cool uncle figure' than 'perky young Autobot warrior'. There's definitely the element of maturity/seasoned soldier to his general character trait that makes him less appealing candidate for Bumblebee substitute...
... but then they somehow thought Mirage was okay, who also have seasoned soldier vibe on top of being significatly less friendly towards human culture or Earth. Yes, he's also less friendly towards anyone in general, as you mentioned how emotionally closed off he is.
Imagine the character potential. A WW1 soldier, the lone survivor of his now-gone noble house and possibly his entire country, who is stuck alone in some bumfuck nowhere filled with primitive civilization of tiny aliens. As he struggles to keep himself alive just one more day in an unfamiliar world constantly hiding from enemies that may or may not be here, his resolve and hope is on the brink of being lost... until he makes an amateur mistake and reveals himself to an unspecting human one day. Accidents, adventure, and tomfoolery ensues, and as the companionship between the human grows over time so does his will to fight on.
There had been so many 'relatable human character and cool robot sidekick' dynamics. When I saw Mirage's name on the roster, I thought perhaps I could expect somthing that was other way round. I still can't tell anything for sure from just trailers, but I fear that we're getting blue Bumblebee/young Jazz for protagonist for this movie. While there is a slim chance that his character would turn out to be much better and complex than that, I suppose we won't get to see any trace of his G1 self in character-wise.
