I think I might make a Ghosts force as my 5th in-house skirmish force. I already have Eternal Wardens, Human Kingdoms, Orcs, and Ratmen, and I had been looking for another to collect that was different enough rules-wise to be meaningful. Beastmen (with a few Chaos warriors mixed in) ends up feeling a lot like Orcs (poor defense and Furious) and visually looking a lot like Ratmen on the table, and the only really good models for a Fyreslayer dwarven force are reeeealy expensive- especially the ranged ones.
But I see you have changed Ghosts quite a bit since I first saw them in the in 1.0, when Ethereal units were way too tough to hurt reliably so they didn't seem like they'd be fun to face off against. But I am a fan of the "improved" version of Regeneration they have now- especially as that was going to be the mechanic that made Fyreslayers different enough to end up on my shelf from the others.
My idea is to make a force mainly from the Ghostly Undead list, but with the Skeleton King brought over from the Vampiric Undead list as a commander (I like that he hits harder and has some better gear options than the Ghost Knight from Ghostly Undead, which I feel balances out that he is not Ethereal like the rest of the Ghostly list.)
Because the model is not Ethereal, the story is that he's going to be a Death Knight who was Lord of a manor that was sacked and destroyed. His spirit clung to the remains of his body, and all the troops from the Ghostly Undead list are the different spirits of his household, called up as he quests for revenge/a way to end his living curse.