I have wondered if this would help Ukraine. Let a thousand balloons float serenely into Russian airspace. Some of them may have drones on them waiting to be cut loose and drop a payload on something important. Or they may be carrying a weighted 3d printed shell of a drone that does nothing, Russia can't afford to take that chance. And likewise in the other direction.

Which way are the prevailing winds at altitude over the Ukrainian-Russian border region, anyway?