Emperor-------->Empress 
maybe have one of the custards unplug the ol' guy, finally releasing his soul from what has been eons of imprisonment under misguided belief, allowing it to incarnate within her, making her the new Saviour (tm) of All Mankind
y'all think the nerd rage would be enough to generate its own warp entity
How I'd make warhammer nerds mad: Do literally anything that changes literally anything about any part of the universe or lore or stats of the units
The only real star marine chapter is Mars. They have the most technology so they can make the most star marine costumes. If they wanted to they could make all the little guys star marines, and the star marines on earth would just have to be like "dude I surrender". There would be way too many even for their tanks.