This is pure ignorance and or thinking it can be done like shown in TV shows or movies. Any bio-weapon that is effective would be a virus/bacteria that is propagated via air particles like Antrax. That's not something you can build in a shed because without the safety precaution the person creating it would be the first victim of it.
I have relevant professional experience but do spout off.
> That's not something you can build in a shed
A negative pressure enclosure, filtration, and UVC sterilization can't be built in a shed? On what basis do you make this seemingly absurd claim? Go check out what hobbyist mushroom growers commonly get up to in their back yard.
BSL-3 is far from technically complex. It's just safety critical to an absurd degree thus (rightfully) mired in bureaucracy.
Don’t even have to DIY anything, the equipment is often found in liquidation auctions for a few hundred bucks a piece. A decent lab can be had with a few thousand bucks and a pickup truck. The harder part is getting proper Sigma Aldrich access for the really interesting reagents.