Removable battery's and SD cards are a gigantic pain for manufacturing purposes.
SD cards in general are a nightmare for support as well, as most consumers will buy the absolute cheapest slowest card they can find, throw in in their phone, and complain that things on their 600$ - 1000$ phone...
I wouldn't purposefully open a gigantic security hole in your phone, but that's just me. What apps do you actually need that require root? Why are they requiring root?
QHD. 4k isn't noticeable, would be incredibly expensive, and has no real benefits in the mobile world. It's a gimmick at best, a battery drain at worst.
So long as they keep pushing security updates in a timely manner, I am happy. My entire business is on that phone and there is no excuse not to push security updates in a timely manner.