Yeah, I see the potential for abuse and also that 99.999% of players would never, ever, ever have access to that kind of tech in a city where even guns are highly regulated.
As I envisioned it though, you would need to have certain skills, mostly tech related, on order to operate weapons of this type or at least configure them. It wouldn't be push the button boom, instant death.
Like I said, a timer on something like a genetically modified insect would leave only a brief window of opportunity, and there could be plenty of ways the assassination could be botched.
I was thinking along these lines in trying to give players that are not at all 'fighter' type characters some offensive ability beyond just hiring some muscle.
But things like this would be cool genuinely cool in the hands of NPCs. There are plenty of places where 'drone' type weapons would come in handy.
Down in the sewers biomechanical rats with high energy lasers keeping out unwanted guests.... or hovering drones patrolling a perimeter around the dome in the badlands. Maybe things like this exist, but I still think insidious ways to die are cool.
Like, you may be a god at fighting and nobody can touch you. But no matter who you are, you get bitten on the neck by a killer bee that injects a bacteriological weapon into your bloodstream and you are dead. For a world where death comes easy it wouldn't come as a surprise if weapons of this type were available if really hard to come by.