Finally got around to ordering that cable and then went over to
Parts Express to see what I could do. A guy there thought the same as you, that the heat-shrink will help but won't stop the problem in the long run. He proposed a great idea though....
-- Buy an iPod extension cable
This way, the expensive ($30), proprietary cable remains tucked away under the dashboard and if the connector on the extension breaks, it's a $7 part to replace.