The real names of the onis in Kamen Rider Hibiki follow a certain naming scheme.
The first syllable of the oni's first name, last name, and oni name are the same.
Here are the known ones:

Kamen Rider Hibiki: Hitoshi Hidaka

Kamen Rider Ibuki: Izumi Iori

Kamen Rider Todoroki: Tomizo Todayama

Kamen Rider Zanki: Zaomaru Zaitsuhara

Kamen Rider Danki: Daisuke Danda

Kamen Rider Sabaki: Sakae Saeki

Kamen Rider Shuki: Shiori Shinagawa(in the case of Shuki, shu is written with "shi" and a small "yu" thus allowing the naming scheme to work in Japanese)

At its early design phase, Kyoryu Sentai Zyuranger was going to have the five don these colors with these dinosaur motifs:

Red - Tyrannosaurus

Green - Triceratops

Blue - Pteranodon

Black - Brachiosaurus

Yellow - Stegosaurus

The reason the lineup changed to what it is now was to avoid the problem of them not being distinct from each other. Which is why we see two prehistoric mammals, the saber-toothed tiger and mammoth instead of a brachiosaurus and stegosaurus in the main lineup(though as we all know they brought back the brachiosaurus via King Brachion/Titanus).

The visors of the Ohrangers except for Kingranger are loosely based off of the Zener cards. The three wavy lines are replaced with a triangle and the X is replaced with two parallel bars. Kingranger's visor shape is modeled after the hanzi(Chinese character) for "king", pronounced "oh" in Japanese.

Would the female have been the yellow ranger of the team?
(I feel like I’m asking an obvious/ stupid question. :o )

This is just a personal theory/assumption but considering that the last team who wore the five olympic rings color(Liveman) had a blue heroine and the show right before it(Jetman) had a blue heroine as well, I think they would have made the Blue Pteraranger the one. As much as I love how Zyuranger turned out, I think this could have worked too.

This only makes me like Garu a little bit more.

He was also Mugen in Samurai Champloo and Toshi in Gintama as well. :)

Never cared to watch Gintama and Mugen for me will always be Steven Blum. So that fact does nothing for me.

Jetman had a non-canon epilogue manga where Ryu and Kaori had to save their daughter alongside Raita and Ako. Because of Gai not being available they recruit a half-American half-Japanese young man named Jeffrey as Green Eagle, and his suit and jet were green repaints of Black Condor's.

Hikari Sentai Maskman alumni Issei Hirota who played the role of Akira/Blue Mask and Yarinin Toppa in Sekai Ninjasen Jiraiya is an actual Chinese martial arts practitioner who has trained even prior to Maskman.

He was Japan's representative in the 1991 World Wushu Championships winning first place for swords and overall second place.
He currently coaches people in his personal classes called Shishin Bujutsu Club(Four Symbols Martial Arts Club, Four Symbols here referring to the Azure Dragon, Vermillon Bird, White Tiger, and Black Tortoise).

His skills also shined behind the scenes of Maskman as he helped his suit actor Tsutomu Kitagawa with his Chinese martial arts moves and also advised in the poses for the Maskman team based on his experience.

Kitagawa later used this experience with Hirota for motion capture work for a video game, Dairanger, and also as an advisor for Gekiranger.

While watching the Ultraman X movie I found some trivia to share.

Guest character Tsukasa Tamaki, the archeologist, was played by actress Takami Yoshimoto. Yoshimoto is a known actress within the Ultraman fandom as the heroine of Ultraman Tiga, Rena circa 1996. She is also daughter to actor Susumu Kurobe, the actor of Hayata/Ultraman which makes the appearance of the first Ultraman and Tiga even more meaningful.

Actor Ukyo Matsumoto, currently known as unlicensed doctor Taiga Hanaya/Kamen Rider Snipe in Kamen Rider Ex-Aid was a regular of Ultraman X as pilot of Xio Hayato Kishima.

Actor Yu Kamio, known to Rider fans as Dr. Kiyoto Maki in Kamen Rider OOO, Yuki's dad in Kamen Rider Fourze, and Yugo Tachibana in Kamen Rider Amazons, was team captain Shotaro Kamiki.