sentai villains: an history; human looking vs suit villains

Hi
Here is an analysis about sentai villains. I'm posting it on HJU, but also here:
In sentai series, the main villain group has a very important role in the story, and they're the ones who lead the different MOTW
During the long history of Super Sentai, the main villain groups have been very different, with human looking villains, or suited villains (either robots, or monsters)
Let's review the history of the main villains of sentai, with an emphasis about human vs suit villains:
First era: Goranger- Battle Fever J: villains groups reminding of Showa Rider series (especially Goranger) : very few main villains; mostly one big bad, who is often a mysterious figure, and one general (in Battle Fever, a second one comes later): a important villain actor of that era is Masashi Ishibashi
- Second era: the Denziman-Jetman era: the villains are mostly human looking, with a few suit villains, who are either monsters or robots
that second era itself can be divided in three parts
- a) Denziman- Sun Vulcan: the Uehara era: most of the villains are female, human looking, and the ones doing the most field work are female spies, who may sometimes fight: Denziman also has a male general, and another male villain coming later: Sun vulcan has a main male sounding suit villain.
That kind of villain group is gonna be used a lot in Metal Hero series, starting with Sharivan
b) GoggleV- Fiveman: the Soda era: Hirohisa Soda uses in his series villains groups having a very characteristic hierarchic pattern:
- A Big Bad: usually a monster like villain, who occasionally can appear as a big human like creature (like Changeman's Bazoo or Fiveman's Vulgyre); in some cases, the villain is a male human mad scientist (Bioman, Liveman)
- One or two human looking male generals: the second in command, and in most cases, the brute-like general
- One human looking female general, who in a lot of cases may have one or two human looking female fighters under her orders
- One or two suit villains (either monster or robot) who can be the comic relief and/or the brutish fighter
- an additional human looking villain; either male or female who brings more conflict within the villain side
- sometimes a monster who makes the monsters big
c) Jetman: the only difference with the Soda era being the lack of hierarchy between the villains
- Third era: the Sugimura era: Zyuranger- Ohranger; Sugimura is gonna try a lot of different groups, and his era is pretty much a transitional one
Zyuranger is gonna use the pattern which is gonna be used a lot later: most of the villains are suit villains, the human looking ones being the female villains and the evil ranger
Dairanger pretty much uses again the Soda era pattern, but with the twist that the leader of the villain side appears pretty much late
Kakuranger's villains has a suit Big Bad (Daimaoh), two human looking male villains (Yugami and Junior, and a female human looking villain group (the Hanarangers) ; but the Daimaoh and his son (Junior) are regulars at different points of the series; Yugami and the Hanarangers are recurring villains
Ohranger has only suit (robotic) regular villains
- Fourth era: Carranger-Go-onger: the main trend during that era is : mostly suit villains, with one or two human looking villainesses, with sometimes one or two human looking evil rangers
Some exceptions: Megaranger, which has a male human looking villain (Hinelar) who is the most important villain of the series; Boukenger which has Gajah, who's human looking; and in Gekiranger, Long, the Big Bad, is most of the time human looking
a few comments:
- in those series, the storyline is mostly driven by the suit looking villains : the exceptions being Megaranger, of course, but also Abaranger, Gekiranger , and in a lesser way, Hurricanger and Boukenger (Boukenger because of Gajah; Aba, Geki and Hurri either because of the villainesses or the evil rangers, or both).
- starting with Timeranger, a lot of suit villains may have formerly been human or human looking: like Gien from Timeranger, Ryuuwon of Boukenger, or the Kenma from Gekiranger, who are the evil counterparts of the heroes's animal looking mentors
- Last era: Shinkenger-Kyoryuger (from what the scans tell us at least): mostly suit villains, inclusing the main villainess; if a human looking villain appear, he's gonna be male and the Red ranger's main rival; however, suit villains having been human or human like before are seen regularly (like Dayu, Robogog, Buredoran/Brajira and Barizorg)
Go-Busters is a special case, with very few regular villains and mostly human looking ones (despite them being mostly data): not unlike the Battle Fever pattern, but looking younger.

Your thoughts? Do you agree with my analysis? Have I made some mistakes?