Its quite safe if it works. The problem is still that you need to handle a high voltage conductor that can malfunction and it can be cut, insulation can go bad, control systems malfunction, etc.
If it was in a industrial setting they would probably check it with a fucking megger periodically. To do it right you probobly need to disable it with contactors (rather then relying on a software safety to depower a H-bridge or something). This means electromechanical parts, which means ware and tear, inspection requirements, etc.
I'd rather get a little bit of warmth from a 480 watt leakage
Pumping gasoline is not that great either.
I have yet to see a problem from my great electric toothbrush.
Personally if I controlled it I would make it so the car battery is removed and put into a hardened flameproof bunker. Preferably by a robot.
I charge my power tools inside of a metal toolbox for this reason, and keep the batteries separated when not in use in different compartments.
A lighting bolt or bad transient can come up on the line and possibly damage the battery and cause a fire or explosion. Particularly as things get old, manufacturers cut corners, etc.
An RF bridge is going to have a intrinsically high isolation against bad transients, and since reactors are probably used, they provide current limiting (unlike a thick ass cable).