I actually apologize - I was way more rude than I should have been as I'd only woken up when I sent that first reply, so I am sorry for that. You didn't deserve me being an asshole to you.
You would be right on the money with your prediction/wish if this were most titles like this; in-context, it would take quite the finagling on the MC's part (and the heroines/their families) to make some sort of polycule work. Plus, the various heroines would also have to agree with it.
But I could definitely see some sort of situation wherein MC helps out our ojou-sama here get out of this arranged marriage, take her father's place as herself, and then just run the family empire without needing to marry. She can have a family later, but on her own terms. Not quite the harem situation, but remaining friends and maybe even "business allies" with MC and the other heroines.