Hopefully Omori plans to use the Freya Familia members in Orario to influence future plotlines. I could see him not wanting to connect future arcs to events related to older ones and especially not Freya, given that her arc just finished.
The reason I say this is because the 20 mid-sized Familia-worth of level 3-5 people is a notable force of people that likely hate Hestia Familia, Bell, and also any traitors from the Freya War Game(Horn, Hedin, and Hogni.) There is also the giant healing force now available in the city.
The former executives are characters that I actually expect Omori to use, but I am not sure for the rest of the disbanded Familia.
That said, a large group of decently strong people that hate Hestia Familia will make the talk of Haruhime being constantly targeted a bigger deal, now that her magic is known. Bell would have to handle a group of people who are weaker than him, but stronger than his allies.
Also, I can see Horn just not being in the story and not particularly mentioned. By contrast, I could also see her being used in some form by Omori.
She does have an OP charm ability via her magic, which is a high stat, after all. I could see her joining any Familia fine, if she isn't a risk due to the remnants of Freya Familia potentially hating her.
If she is targeted, joining a sufficiently strong Familia could protect her. If that doesn't work, maybe she could seek refuge with some group that could find her useful or is willing to protect her.
Hermes Familia might find some use for her while arranging for her to not officially be aligned with them.
Former Freya executives may be willing to help her.
Hestia Familia members or Hostess of Fertility members might protect her if Bell or Syr advocated on the topic.
Alternatively, she can rely on her charm ability, but I'm not sure charming people flagrantly is something Syr would currently approve of, so Horn might avoid that option on purpose.
If she ever works with Hestia Familia, she has some notable uses:
Her high magic stat would be good for Welf's indestructible magic swords as they are dependent on the user's magic stat for damage and mind reserve for ammo.
*Her charm can apparently body monsters at low levels, so she crushes entire crowds of monsters stronger than her via charm. This is odd enough for a level 2 to be able to access, but Omori has written abilities that ignore level gaps elsewhere, so I guess this is fine. I say this because of the Monsterphilia stuff showing that Freya can charm monsters.
*Also, she could buff Bell by using charm on him thanks to his new skill (Vanadis Tevere). This could also be healing if that part is dependent on charm.
Another random thing is that she is effectively an oculus that specifically connects her to Syr, meaning that instead of using a magic tool or letter, it is possible for people in Orario to learn of the situation with Horn's party quickly. The reverse is also true, people allied with Bell can tell Syr something to effectively tell Horn the same information.
Horn is relative in level to the current Hestia Familia members, so she could keep up with them.
*Charm may not be available given the thing I mentioned above.
I would imagine Heith isn't gonna be too notable. She didn't seem to have anything about her character other than being a devoted healer of Freya Familia. She might opt to follow old members to continue healing them, or do something like join a healing Familia such as Dian Cecht (probably not the Miach Familia that aided Hestia Familia.)
I would enjoy seeing Van be a character like Luan or Mord, in that he is not prominent but is occasionally mentioned or participates in big events.
Aside from that, considering that random Familias would likely get stronger following the Freya Familia's property, resources, and members being taken, I hope we can see more new strong Familias start to develop.
I also hope some use for anything Hestia Familia claimed is given. If they got money, hopefully they can afford materials to properly equip armor and other supplies to Bell and Ryuu. They are at levels where their equivalents in Loki Familia would specifically get custom order equipment by their contract blacksmiths, after all.
Personally, I would enjoy if Ryuu had a contract with the current captain of Astraea Familia, as that would connect her with the new generation of the Astraea Familia. Any property claimed by Astraea following the game could go into restoring the Astraea Familia in Orario, developing it outside of Orario, or helping Ryuu.
Also, hopefully Miach Familia can offset the debt they have to Dian Cecht or pay off the repair costs of Naaza's arm being re-destroyed with their new money.
