I don't think Guyver is that sort of manga.
What do we know about our protagonists, even after all this time? Almost no details from their personal life at all. It's all drama.
Even Mizuki, who is as normal as it gets in Guyver, is rarely if ever shown doing anything that is superfluous to the story.
Have we ever seen anyone read a book, watch television or play a video game?
This suggests Zoalords have down-time, too (After all, the only real problem they ever deal with is Guyver-related... well, and now Apollyon-related) and I doubt they spend it all standing around as clothesracks for enormous capes and shoulder armor. We just never see them do whatever it is they enjoy.
Dr.Barcas: Likes to putter in his bonsai garden.
Shin: Reads. Recently finished 'Cien años de soledad'.
Yentsui: Amateur stage player.
Waferdanos: Liked to fly.
Guyot: Predictably, he used to love competitive sports, especially tennis. Unfortunately those are out now because none of the other Zoalords play. He's trying chess now.
...Is the sort of thing I mean.
That being said, there are several female protagonists in Guyver, the one closest to being a separate main character being Valkyria. And, again, we only ever see her in action or when she is reflecting on occurrences in her life that are relevant to the main story. Could you imagine her putting on make-up? It's just not that sort of manga.