Your fabrication skills are excellent and are matched with fabulously well thought out designs.
I have thought about trading my '07 525 EXC for the new 500 EXC but I cannot see a clear advantage to my well set up 525 (now a 565) so I am watching this thread to see how the new FI works and how you think the handling compares to the older 525 design. My dealer said of the FI to just forget about it failing since it is well proven now. "If you are going to stress about this just get a spare injector and carry it in case the stock one plugs up from crappy gas."
For those who worry about engine reliability I would note that I ride with a guy that has an '07 525 EXC with 16,000 hard DS and racing miles on it. He just changes oil once in a while. Since he is finally running to the end of his adjustment on his intakes he is going to go with K-W stainless valves. (The valves in the new 500 should last as long as the K-W valves.) One engine builder I talked to said that most of his 525 engines go at east 30,000 to 35,000 miles without ever needing any work except checking the SS valves once in a while. When I asked him about oil changes for DS riding he said, confirming what FTB said, "Oh, just change it when you can. 1,000 to 1,500 miles. And run good oil. Motul or Rotella T. The HT oil cooler is nice but probably not needed for DS riding. You probably won't be hammering up long, steep sand washes."
For those that worry about sub-frame damage I can only say that I have tested my stock one in every possible way without damage. I watched one guy flip his 525 MXC on a double jump with it landing on the rear end of the sub-frame. He broke his rear plastic fender. The 500 should be just as reliable.