Having an emergency shut off on your winch is a good idea. I almost burned my winch up when a solenoid locked open when pulling up the hill and had to pull the battery. If it was me I would put the switch under the hood and just leave the winch on full time. I have never had my winch run off on it's own on me and it saves time when winching. Roadless Gear has a winch control setup you can easily wire into your winch for in dash control you might light to check out
over here.
When you wire it, I would go to the top post on the battery instead of the side. The side posts are usually connected via a copper strip to the top post. If it is a cheap battery or your connection is a little loose you will generate to much heat and melt the side post off.
For the winch, I would reach up with a welder after everything is bolted down and put a tack on a bolt or two. That will stop interested fingers from walking off with it unless they are carrying around a grinder in their back pocket.
