The only physical thing I would change is milling the catch cup completely flat with the top of the device. That extra 5-6mm would please me very much, though not a big deal. The biggest change I would like to see is a larger bottle inside. I am using the 9ml bottle from a Vapage, but don't really care for the small top cap on it. Just makes it harder to refill. It would be better with a larger mouth on it. As to the 26650, it has been discussed a few times in the past year and in general, not needed. With the evolution of batteries lately, I have found I only change my battery once a day as it is right now and I vape in the .2-.4Ω range. The 26650 would just be too bulky and heavy imo...