Thank you very much!
It's still work in progress at the moment but I'll let you know as soon as it's finished. I'll be putting it up on the Great Library for anyone to view when it's complete. I'm also working on Warhammer: Tilea and several other projects at the same time, all of which are largely being put on hold at the moment due to University work.
Regardless, I've been looking at other sources for Slayer armies in the past (including the 6th Edition Dwarf army book and Storm of Chaos) and I'm going to build upon these and the Fyreslayers to produce a diverse army list for the Cult of Grimnir. Generally I plan for the army to be strong but not ridiculous. The initial weakness of the Slayers to start with is of course their lack of armour, but I plan to include quite a few methods in which units in the army can get Ward Saves, more than most of the GW Canon armies as practically all of them wear armour, to counter this so that a Cult of Grimnir player can get his army across the board without it getting shot to pieces. Also I've pictured the Slayers to be quite archaic compared to regular Dwarfs, so they will have no black powder weapons at all but will have access to a variety of different creatures and also the traditional Grudge Thrower and Bolt Thrower, as well as the legendary Malakai Makaisson's Goblin Hewer. Also included will be a smattering of regular Dwarf units such as Warriors, Quarrellers and Hammerers, as the Slayer Keep was also home to non-Slayers, but the army list position of these will be notably different to reflect the more melee-oriented Slayer army.
Also fluff-wise I'm keeping largely to the Warhammer Fantasy fluff but I've also been researching stuff that comes from Warhammer Fantasy Roleplay concerning the mannerisms of the Cult, as there's a page about it on Warhammer Fantasy Wiki that is all about it, and most of that data comes from WFRP. Also I like the idea of them searching for Grimnir that comes from Fyreslayers lore, as Grimnir was 'lost' in Warhammer Fantasy too except that nobody is sure if he's still alive or if he's dead, unlike AoS which spoils it by saying he's dead. This would then give the Slayers a 'goal' lorewise other than just looking for glorious deaths, so I'm keeping elements of that in.