Oh yeah, true that! I also noticed some CO's having different demeanors than their OG counterparts. Like you mentioned, Andy seems less naive and more unused to knowing how everything in Advance Wars works. Or maybe that's just the way he comes across in his animations? Likewise with Nell, she seems less mature/adult-like than she was in the originals and leans much more to the "kawaii/anime" side of things (also looks younger).
They did seem to completely remove the self-insert advisor role which i'm a fan of. It just makes dialogue weird with the CO's talking to you, the "advisor" much like FE7. I think Andy is going to sub in for the self-insert which is totally cool in my book, Maybe due to him being apart of Field Training is the reason why he's less dumb? IDK lol. I totally want to see them subvert everyone's expectations in the "what's an airport?" scene. Like, Andy could say that and then be like "sike of course I know what it is sillies!" and i'd love that. Or maybe just pretend to not know stuff to tease Max & Sami? IDK lol. It did say in the trailer that this game is a "re-imagining" of the GBA titles so I could see them taking creative liberties here and there with the story.
I'm not too familar with WayForward stuff but from what I hear, the Shantae series is really beloved from them so I trust them with these remakes. Maybe after this game, WayForward could create a new Advance Wars if IntSys is too busy working on Fire Emblem.
In regards to Smash Bros, you could go about that either with an individual CO or the entire Orange Star trio. My personal preference is for Andy to fight solo because having the attention on one CO helps build attachment to that one character for the player. Also, I feel like the three characters function too differently. Andy's moveset kit would have a heavy focus on repairing damaged units and wrench melee attacks whereas Sami is more of a Snake-esque fighter with her hand to hand combat and focus on her machine gun melee attacks. Max I feel would be a Falcon-esque fighter so he's probably the most unoriginal of the three.
That being said, i'm not opposed to the idea. I've seen some
moveset ideas that have the three as a trio working together which I kinda liked. And with Pyra/Mythra being a two in one fighter, it's not out of the realm of possibility to have a three in one fighter in Andy, Sami, & Max. I just like the idea of Andy running solo with Sami & Max in some of his moves. As long as Advance Wars is represented in Smash, then i'm good lol.
Speaking of which, here's my custom
Challenger Pack for Andy I did back in November last year. Check it out when you have the chance!
I'd definitely be down for more character interactions between the CO's and having more focus on the characters. Hell, you could even have a mode where the focus is on the CO's somehow like a dossier of the CO's and their detailed backstories of how they became CO's and why. They could also continue on with what AW2 and AWDS did with having neat artwork of the CO's together and/or interacting with each other.
You were added to the support list some months ago (check the OP). That being said, I love the idea of a Black Hole pallet swap for any of the CO's that are in the game, whether it be Andy or the Orange Star Trio.
and Metroid are finally starting to run out of major candidates to include. Only real thing that'd get in AW's way at this point (besides flopping) is a resurgence for 
