If Magis had survived, he would've become this Sentai's green warrior, just like his actor did six years before...
Dawson Casting: A tie-in booklet for Shinkenger vs Go-onger gives the Goseigers' ages, which leaves 18-year-old Kyousuke Hamao playing 21-year-old Agri and 20-year-old Kento Ono playing 24-year-old Hyde. However, the trope is played straight with 20-year-old Mikiho Niwa as 17-year-old Moune.
The Leon Cellular, Gosei Knight's phone, may also sound familiar, particularly since it speaks English and attaches to a gun that can turn into a sword. It shares the voice of Cross Mirage, Teana's gun from StrikerS.
What Could Have Been: The original plan for Goseiger called for there to be more of a rivalry between the different heroes, hence why they were split into different tribes ala Chou Sei Shin Gransazer. The Skyick Tribe (Red and Pink) would have been the idealistic straight heroes, the Landick Tribe (Black and Yellow) would have been closer to Anti Heroes and clashed with the Skyick Tribe a lot, and the Seaick Tribe (Blue) would have either been a Wild Card or a neutral arbitrator. While this was scrapped before the show even started (so the team pretty much gets along from the start), you can catch occasional glimpses of it from the way the characters interact with each other.