I'm sorry you're frustrated. It appears that you've found someone who has more information than I do. I'd recommend contacting them directly for the information you're looking for.
As far as a simple upgrade kit, I still think that you're looking at replacing several lines. Perhaps all you will need is the front lines for a 2015 bar. I really don't know. But before you get angry at me or North I'd recommend you wait and see what North offers.
As far as single vs double lined safety I feel I'm flogging a dead horse here... You can check for previous posts on pluses and minuses of each system. We felt that the way our kites worked in the past the double-front line release was more safe. Early Evos would go into a death spiral when released onto a single front line. For some reason it appears that the same issue does not happen to newer kites, as such we are moving to a single front-line release. We do our best every year to make the gear as good and as safe as we possibly can. We also do our best to keep our gear as backwards-compatible as reasonably possible without overly hindering design progression.
-Dan