that well paved road

The first obvious roadblock is that, in all cdramas and kdramas i've watched so far, THE big cliché is the following: "you and your wife didn't manage to get a son? take a concubine"

And obviously if Mr Bennet - er, I mean Mr Ban - had five daughters in a row and didn't have any son, the obvious solution would be to take a concubine. Even if he isn't putting any money to the side, he owns his own house, so at the very least a servant girl or some other lower-class girl would be propped by her parents to become his concubine, even if it's not as advantageous as being the concubine of a man who knows how to budget and whose wife isn't Mrs Bennet - er Mrs Ban, er, Gang-shee, since a married woman would still bear her maiden name iirc.

Two solutions to this (not necessarily exclusive):

Mr Ban had a son, but he died just before the events of P&P.

That means he didn't feel the need to take a concubine prior to it, and explains why the heir to everything he owns, Mr Collins, or here Mr Gaolin, didn't appear in the picture earlier. Yes, Mr Ban could have just adopted Mr Gaolin as his heir years prior, but if he had a son, it's not necessary.

Mr Ban actually did take a concubine.

Whether or not she is still alive could be played both ways. Biological mother or not, all the children born of concubines are supposed to call their father's Main Wife "mother" anyway, and obey her orders over the ones from their own mother. Her matchmaking wouldn't change much either, she's supposed to take care of the marriages of all the children of her husband whatever their mother. In an effort to simplify, I would have the concubine dead for some years (or Mrs Bennet was the concubine, taken in for her beauty if not her wit, and the now-deceased main wife was more Mr Bennet's speed; but with her death, Mrs Bennet became the Main Wife? idk) (we're going to go with Mrs Bennet as Main Wife all along for this)

In that second solution, it means there are (at least) two mothers for the five daughters. The obvious split would be to have Lizzie and Jane be full sisters, because they get along so well, but I think it would be unlikely. If there were two wives under the same roof, it makes more sense to me that the two pairs of sisters born less than a year apart, Jane & Elizabeth and Kitty & Lydia, would be split in the middle. Jane and Lizzie wouldn't have the same mother, and so on.

Which gives us two possible repartitions (ignoring Mary for now):

Jane & Kitty were born of the same mother; Lizzie & Lydia of another.

Or, Jane & Lydia born of the same mother, Lizzie and Kitty of another.

Of course then comes the problem of which mother is which. Lydia is generally favored against Kitty by Mrs Bennet; so Lydia would be Mrs Bennet's own daughter, and Kitty the daughter of a concubine. Given that Mrs Bennet also emphasises (though we have no reason to think it's not true) that Jane is the prettiest of them all, and we know Mrs Bennet was/is quite pretty herself, Jane and Lydia as her daughters it is then! And since she's already getting n°1 and 5, she might as well have all the daughters with odd numbers. Mary will be her daughter too. Lizzie and Kitty as daughters of a concubine who passed away since, both very close to their closest-in-age half sisters, Jane and Lydia.

(i am sort of partial to Mary being the daughter of a concubine n°2, and her self isolation and constant judging of everyone being a result of being the only one without a full blooded sibling in the tribe; but i don't feel like getting too complicated)

Lizzie being the daughter of a concubine also plays in the very cliché trope of the illegitimate/adopted/concubine's daughter being not only the underdog main character, but the one who marries best, which is kinda neat since i'm going more for vibes of Cdramas than actual correct chinese history/etiquette. And being the daughter of a concubine not a main wife adds to both Collins and Darcy thinking that there's no way she could reject them.

(relatedly, Lydia, legitimate daughter of Mr and Mrs Bennet, would then be dishonoured by Wickham, but Darcy's intervention would be to force him to make her his Main Wife instead of just giving her a concubine rank and going on with his day)

My first thought it how did Mrs. Bennet become the main wife? Because a big part of the plot and how her younger daughters especially aren't well-mannered is because she's lower class. Not low enough to disqualify her from being married to Mr. Bennet/Ban at all, but low enough for people to take note of it. So either Mr. B went against his family's wishes or both B. elders died before they could make a match for their son and he did it himself. Anyway, maybe this doesn't matter but it's interesting to me. (Everyone in town is like, "SEE! This is why your mother decides for you!")

I think Elizabeth being the concubine's daughter and "winning" does play into fun Cdrama tropes. I think by favouritism, Jane and Lydia definitely are the bio daughters of Mrs. Bennet. Kitty being close to Lydia as a way to suck up to Mrs. B is also a good dynamic. Mary is Mrs. B's but still kind of an outsider because she doesn't match well with her mother.

Interesting angle to explain the difference in education and manners between Jane & Elizabeth and then Kitty & Lydia, is that the concubine/side wife (I know the ranks changed in different eras, this is not my specialty) who had Elizabeth & Kitty was properly educated noblewoman and Mrs. B was happy to let her do the work and educate J & E, but she died before Kitty & Lydia were old enough to benefit. She could be a Mr. B maternal cousin whose family fell into poverty/died? Mr. B is her best option because she doesn't have protection and at least it's a roof over her head...

As for why no new concubine after she dies, Mr. B is very lazy and he hated the bickering? Maybe Mrs. B constantly talks about how Jane is so beautiful they can get a good man to marry in? Or, my favourite, Mr. B was kicked by a horse and knows he's not fertile anymore (you could also give him a high enough fever, etc. measles used to do this). If both women stopped getting pregnant after dropping babies like clockwork, the writing would be on the wall and no number of new women would help. (This happens in the novel Love Like the Galaxy, the one family has 13 daughters and then clearly the husband became infertile, he ends up adopting the FL's brother).

I do not know how the Mr. C thing would work. Maybe Mr. B just can't stand to adopt him because he doesn't want him in the house? I have no idea if there is an equivalent to an entail in Qing dynasty China.

Hope this helps! It was a fun thought experiment.

—

Athena Parella, “Quiet House”