To access the necrophilia scenes you have to steal the body, it will then be in your weapons and you can interact with it to either equip it as a weapon or to sexually "use" it. I only like M/M content so I went out of my way to figure this out for you :P
I suppose that as long as the corpse weight to your strength ratio is good enough, that you could use the corpse as a "blunt weapon" and swing it around by the ankles.
