[RX-78GP04G Gerbera]

Well, the whole point of the series is to basically be a middleman between the end of Mobile Suit Gundam and shows what triggered the events that lead up to Zeta Gundam, which it effectively accomplishes by showing how the Titans first got established, technology bridges (like the panoramic monitor/linear-seat cockpit, like 0080 did, and also, with the GM Quel, the earliest bits of the movable frame that eventually becomes the new common MS frame after the Gundam Mark II), the influence of the Dendrobium (unused Plan 303 Deep Striker for the S Gundam of Gundam Sentinal, the Victory 2 Assault/Buster, and such), and so on.

Kou probably comes off as bland in that, unlike a bunch of the flashier Newtype pilots or pilots that more stand out like Yu Kajima (with his involvement with the Blue Destiny and EXAM System) or Shiro Amada (his whole "no-kill" policy and love-influenced actions) of UC (or the pretty boys/flashy pilots of most AUs), Kou is just your typical grunt soldier that just happens to find himself landed in the Gundam's pilot seat after a chaotic situation. He's not meant to be a super-flashy pilot in any way, but just an ordinary soldier just (trying) to follow orders, but with no real idealism like someone like Shiro or Gato displayed. As Gato called him, he's just "a cog in a war machine", going about like little more than a drone with no real purpose besides blindly serving the Federation.

For Gato, what else do you expect for those who were completely brainwashed by warmongering, dictator bigots like Gihren and the Zabi family? It's not like he's the only one affected by it either. He's basically one of many fanatical followers of the Zabi belief, much like how many Nazis were of Hitler or suicide bombers and such. It's really nothing out of the ordinary in such a case.

Kelly also doesn't come off as that strange, especially when you consider he went from a war veteran to a junk yard dealer after losing his arm and the war ending. Anyone who believes their life is so bland/unfair/etc would want to have some sort of higher calling or purpose that they can accomplish themselves or at least have a part in it and Gato gave him that by offering him a position in Operation Stardust.

Nina's the only thing I really agree on (even Cima gets more known background, lol), given the whole love triangle that shows up out of nowhere near the end and never really gets explained but I'm willing to let it pass as it doesn't really have any impact on the UC story as a whole and, as said, the main purpose of 0083 is establish the link between MSG/0080 to Zeta Gundam, which it does. E