maybe I should organize a primarch duelling minigame at my local GW

just say that you can use any primarch, the plastic 40k ones can be used as their 30k equalivents (because it's a GW and they're averse to anything that excludes 40k) (except 40k mortarion go fuck yourself I guess) and maybe some other stuff like greater daemons as sovereigns

all using challenges and the gambit minigame to see who comes out on top, with players betting on the winner of each fight before dice are thrown