Probably take more than a toggle switch, some of the wires carry a lot of current and the heat produced would likely destroy a toggle switch, in cases like that best to use a toggle switch to actuate a relay that is rated for the current.
On my 98 Royal Star Tour Classic the ignition switch was located on the left front just behind the radiator so it got plenty hot. My ignition switch went bad while the bike was under warranty so the local shop replaced it for free. I am not sure if new switch modules are still available or not for that year bike, if they are I would replace it, if not look up Dion Hinskey here on the forum, he makes ignition bypasses for the 1999 to 2013 Ventures, he may be able to help with one for your year and model.
Here is link to his profile, https://www.venturerider.org/forum/profile/6542-djh3/