nothing would prevent putting a nuke on the drone, and making a it a tactical nuke delivery system. you can have them as big or small as you want, and in air, on the surface, or under the water.

you are applying arbitrary constraints to a thing thats just "put an rc controller on it"

ukrainian drones are doing something like 700 miles to hit the oil ports in primorsk. its not the 2500 miles that a missile might do for hitting diego garcia, but nothing says you could get one to. after all, a b2 bomber can go on long flights. put controller on it, and control it via a satellite, and the b2 becomes a drone