I've thought about something like this but been concerned about the
potential for singing and damage. I've sometimes seen a vortex coming off
the keel with enough energy that the water has cavitated, boiled into steam
at seawater temperature due to the low pressure. The prospect of rope or
wire, and metal fittings screwed into the fiberglass standing up to this
much energy doesn't seem like a good bet to me. Grounding could put
enormous strain on the cable, one end of which is attached to the rudder.
If a pot warp ever did get around it, it would be an incredible snafu.

I've found this method for disentangling to work very well the two times I
have resorted to it, and those were without practice. No swimming or
cutting involved. You should have this equipment handy and always try this
first. Even if it doesn't work, it will set you up for safer and easier
attacks by other means.

http://home.maine.rr.com/rlma/Pots.htm

Now that I've done this a couple times, I expect to be able to get
disconnected with not much more time or trouble than stowing the main.

All three times I've fouled, it's been pots that were twisted around
themselves and not lying naturally. I now watch for pots unusually close
together or which look like their warps are unusually tight.

--
Roger Long