Yeah I kind of like that idea too. It has the potential to be extremely dangerous, because if you pass out in the open, you are done, the fungal creatures nearby will kill you while you are passed out unless their AI is changed. But it is a sort of limited danger though.
Going anywhere near Mycus with sleep spores without a gas mask or environmental protection would be about as safe as visiting Bill Cosby’s hotel room. But if you have hazmat gear you would be fine, and they would be no more threatening than normal.
To address this, instead of spores you might have them shoot sleep darts at short range or have the substance injected by a fungal mycelia tendril or something. Make them inflict fatigue and knock you out if they manage to get enough shots that pierce your armor, and if you don’t take a hit of a stimulant or atomic coffee or something.