The Rising Gundam's overall motif is that of the samurai's wife, who defends the homestead with bow and naginata. It makes sense for Rain to use it, except that the show says it was made for Ulube, and Rain appropriated it.
The naginata is traditionally the weapon of a samurai's wife, yes, but the samurai himself was just as likely to use a bow (in fact, the longbow was originally their signature weapon, before the katana was even invented). And it wasn't until the Edo Period that the naginata became associated with women; for centuries beforehand, it was a common infantry weapon.
Domon is the only Gundam Fighter that doesn't look like an ethnic stereotype... until you notice that he's a martial artist obsessed with family values and honor, and that his Gundam has a fairly stardard look because the average Gundam always looked like a Samurai.
Also, Neo Japan itself picks up the slack quite a bit when the Devil Gundam takes over the entire colony, effectively turning it into a giant tentacle monster.
If every Gundam fighter is a national stereotype, why is the German fighter a ninja? Because he's actually Japanese. In other words, he's a Japanese stereotype disguised as a German stereotype.
The original Schwartz dressed the same way, though, suggesting that he was also a German McNinja.
A little something from Mobile Fighter G Gundam: Domon's crest may seem out-of-place, but come the last episode, it makes perfect sense.
Towards the end, Ulube calls Domon the Knight in Shining Armor to rescue his princess Rain from him, the evil sorcerer. Usually, there's another obstacle for a knight to his fair damsel. Look at the remains of the Devil Gundam at the end, does it remind you of anything?
During the Lantau Island Battle Royale, Chibodee and George, who represented Neo America and Neo France, respectively, teamed up against the Grand Gundam, which was piloted by Neo England's Gentle Chapman. This could be a nod to the Revolutionary War!
When Gentle Chapman reappears in the finals, his wife Manon, who was intergal to his character is nowhere to be seen. She's probably unaware that the Dark Army reanimated his corpse. She has no idea they went grave robbing and are using his soulless body to try to attempt complete genocide. And she loved him so much...
Another one is the Mobile Trace System that follows the pilot's movements in combat. In several fights we see some of the Gundams get dismembered, decapitated, impaled, and more. Now remember that the pilot is feeling these attacks.
As fearsome as the Devil Colony Gundam was, just remember that was when Rain was the pilot. If Allenby had been put there as Wong planned, that would've been it for humanity.
Politically speaking, Neo-Japan is going to be in a terrible situation in the aftermath. Even if Ulube had gone rogue, the Devil Gundam was Neo-Japan's creation to begin with.
Since G Gundam is the one of the two series in the franchise that employs nanomachines, this is likely the series that led to Turn A Gundam.