Why stop at one?

A nationwide fleet of illicit, unregistered hexacopters that sling 10 GPUs, a server, and LTE connectivity. Upon discovery, they fly off and find other power lines to mooch from.

If it can generate enough revenue from Bitcoin mining that it can pay for it's own spare parts / maintenance, then it's truly self-sufficient!

Especially when the factory that makes them is also autonomous. The trick then becomes self-replicating done factories.

Miner? That's short sighted. They'll likely attach some AI that collects intel, because electricity theft is quite illegal otherwise, so one would be using such a nuisance drone against an adversary. Send'em to Russia or China to watch out for threats.