I see your wisdom. I'll put a 2up connector in line then, solder, shrink, click, done.The wire is not connected because you will probably want to cut it depending on where you locate your switch and also having the break in the wire close to the nav unit makes it easier to remove it if you chose to.
For the factory look i would recommend an Air on Board switch. other than that, any SPST switch will work.
I have my switch already for turning on camera mode. My question was about a dial/switch to select different cameras/sources. I think you're already answering that question in due time though. Thanks.