The most interesting thing I think is that in Jean, Oona? (It's a while since I read it) and Alison we have the prototypes for Jo, Madge and Robin. The younger girl or woman (Jo, Janie) with the older sister/parent figure was EBD's favourite grouping.
And we have the masterful doctor, too! (And is Matey a much softer, watered down version of Morag?)
Apart from the school setting, everything that would become essential to EBD's writing is here, just not yet fully developed.
I hadn't thought about Jean and co as the prototypes for Joey and co, but you're right. Less idealised in some ways, though - but hard to say whether that's a function of it being an earlier, serialised novel, or because it's not specifically aimed at younger readers? Jean and her aunt aren't always in full accord, their puritanical servant bullies them, and Allison, if she is (as I suppose she is) a sort of prototype for the Robin, is a thoroughly un-idealised little girl in comparison - plain, spoiled by being too much waited on, not initially appealing in manner, and shockingly Godless!
Morag, if she is a kind of pre-Matey, is a much darker character - dour, racist, rude, obsessed with hellfire etc. And the CS pupils and staff's 'wholesome fear' of Matey is a much weirder situation in Jean of Storms
, with Jean and Oona, despite being Morag's employers, being terrified of her, to the point where Jean tries keep either Mollie or Allison by her side after Allison and Moti's arrival, because Morag won't go on the attack in front of them....