Sledgehammer is a one-page PocketMod style zine that is inspired (a lot) by Warhammer. It does a surprisingly good job of distilling down the source material, even including rules for momentum in its combat rules.
Mechanically you're rolling under a statistic on d100 with positive bonuses for your career, equipment and circumstances. You have four statistics (Weapon Skill, Initiative, Toughness and Fellowship) that you roll on 6d6.
Careers give you a bonus 5 to one stat of your choice and three things that you know about as a result of your career (later referred to as Expertises).
Checks are Risks and generally you are trying to roll under the relevant statistic. Expertises and relevant equipment both give a bonus of 10 to the number you are trying to roll under.
In combat skill rolls are the same (which might lead to genuine Warhammer 1 wiffy-ness) but elegantly the tens digit of a successful attack is your damage in Wounds of which an adventurer has six. Toughness and Armour don't deduct from damage.
Corruption is quite interesting and effectively replaces Fortune in more recent Warhammer editions. You gain Corruption when a Daemon hits you in combat or you can choose to take a point of Corruption to survive after a fatal wound, to gain +10 to a roll or to heal 1d6 wounds outside of combat (regular healing rules are not given). Corruption is a simple countdown clock with six segments.
There are no rules for advancement or monsters but what is there is surprisingly complete and close to the heart of the original Warhammer rules. I think they're maybe too close and maybe you want a contested combat roll and Fate points but I guess the point is that you've got a minimal hackable system that you can work with here.