That gundam that saved young Setsuna's ass in the opening scene is none other than the original RX-78-2! I think it's no random mobile suit, it's probably going to be a "Chekhov's gundam" that will re-appear in a flashback arc which is comparable to the one that this show's director Seji Mizushima used in the Fullmetal Alchemist.

The only annoying things in this show right now is that there's too much "fairy dust" emitted from the GN drive and now, purple explosions! I think it is ruining the show's realistic premise and mech designs which is commended as a significant departure from the fantastical elements of previous Gundam shows.