First we have to wait for Wesley Crusher to be born, so he can invent the things. 22nd or 23rd century if memory serves.

Second: gunpowder hasn’ t been used in weapons for years. It produces too much smoke. Its hard to see what you’re shooting at through a dense cloud of smoke. Smoke also tells the enemy where YOU are.

Third: I’d worry more about the nannites being used as weapons to eat everything. That would be easier to build than a selective machine. Self-replicating nano-sized machines could devour the earth. This would be bad. Very Bad.

That is called Bio Germ Warfare.
Think of a better way to kill peoples and some tax collecting agency will figure out how to exploit it.
There was profit in Detante, there is more profit in war.