“YJ4” became a thing because those four were the only ones who made it past Graduation Day. But yes, I agree with you in general. On Arrowette: Cissie King-Jones retired during PAD's run, so I don't have a strong motivation bring her back; though both versions of the team had a female archer, and i wouldn't mind carrying on the tradition. I'd rather go with Mia Dearden, though.
As for Secret: I'd love to see her return, though not necessarily as he was. I kind of like the way that the TV show portrayed her in the one episode where she appeared. That, and you could get creative with her story. I may be the only one, but I really like the idea of her brother Harm ending up as an Indigo Tribesman instead of being murdered by his father. He's got the right temperament to be recruited, and it would give YJ a ring wielder without giving us yet another Green Lantern. Plus it would give Greta another tie to the team.