Mini-campaign idea: Dark Inheritance

I now am itching to run, at some point in the future, a "domain inheritance" game in ACKS. The PCs would be heirs to a haunted coastal castle and a dilapidated hamlet (Market VI, I'd say in ACKS terms). In its shadow there would be several lairs/mini-dungeons in the same 6-mile hex. There would be a "Kilodungeon" including the castle and several levels beneath it, probably culminating in a Lovecraftian monstrosity (Aboleth?) beneath sea level, not to mention nasty neighbors such as bandits. Could be a wonderful campaign. A mini-setting - so much to do in one hex and the neighboring hexes!

This will probably be an old Marquise's keep, now fallen to disrepair and haunted. PCs will end up with a potential high-value stronghold, which will need clearing of horrors - and expensive repairs.

To become full-scale lords, the players will need to conquer the castle from the eldritch horrors.

To gain the whole 6-mile hex the players will need to clear out several mini-dungeons.

My inclination is towards a combination of "Gothic" and Lovecraftian bestiary for that mini-campaign. No goblins, but possibly toad-men or fish-men, and a good amount of undead. And bandits, of course.

Potentially a vampire, but the problem with a vampire is that vampires are villains who tend to dominate a campaign, as in Ravenloft/Curse of Strahd, and I want to keep that role for the Aboleth (?).

My general idea is that in the distant past, the (now ruined) castle was home to a Chaos-worshiping Marquessa inspired by Elizabeth Báthory. After she was slain - by one of her intended victims, no less (now canonized as St. Lena of the Dagger) - her heirs continued the Chaotic tradition, albeit in other ways than bathing in the blood of virgins.

The PCs' ancestor conquered this keep, but eventually these ancestors also succumbed to Chaos worship, seeing the local Aboleth (?) as a "God".

Successful PCs will quickly get knighted by the local ruler who would be glad to have them deal with bandits (and worse) than requiring his limited military forces do so.

Of course, the Marquessa would have risen as a Ghast for the very least, it not a Vampire, in the crypts below. Now she has worshipers among the bandits and villagers, like the Aboleth has.

The idea is to make most permanent magic items unique in this adventure. Some are powerful - for example the Dagger of St. Lena which allows you to backstab undead (possibly even without having this as a class power).

What do you think?