>>96176273
First, it probably has to be a separate game. 40K/MtG/DnD are the containment games to keep all the worst people out of other games. You could tout it as being like 40K for adults.
Then, insert stuff competitive players will hate. Random terrain tables, NPC monsters/aliens attacking passers-by, random event tables for stuff like rain and solar flares, units/characters being able to level up, etc. It will be unbalanced but as with games like Necromunda it would be up to individual leagues to enforce decorum for their campaigns.
I don't think it will happen though. When AoS first dropped it tried to be a beer and pretzels game. It had rules like "shout a war cry to re-roll your hero's misses" and encouraged players to just use a reasonable amount of models and then give the losing side some reinforcements. And then you had all the interesting 40K variants like boarding actions that the fans just totally ignored. So in GW's eyes they get punished by the playerbase when they try to have fun and expect gamers to act like reasonable people.