Harcus - Great thread, thanks a bunch for getting it started and your efforts so far
I've been adventure riding a KTM 525 through Southeast Asia for a few years now and looking at the 500 as a replacement if it can withstand the vigors. So I'm subscribed to your thread with baited breath.
One thing I noticed with luggage brackets is they always would end up breaking and usually not in convenient locations. I ended up fabbing these brackets up for the 525.
All the times I broke prior brackets it was where the top left portion of the bracket (in the pic) connected to the chassis. I made some minimal brackets to see if I could reduce the leverage that crashes put on the brackets. Once I fabbed these things up I never cracked or broke a bracket again. The idea is that the bracket only keeps the saddlebag out of the wheel and not used for load carrying. Also when crashed the weight of the bike laying on its side puts a lot of load and stress on brackets causing failures. These small brackets I believe, when crashed had very little leverage placed on them in comparison to standard brackets as they were flush up against the sidepanels, muffler and airbox.
I used the brackets with DirtBagz and sadly this bike is on its side a lot, luckily 3 years and no bracket issues. You may be looking for something completely different for all I know but thought I'd throw it out there for you to peruse.
Best of luck with the 500 and curious with what you and others come up with on this bike.