I don't get why you'd likely end up in the middle if you can select a seat. Are they planning on blocking most seats, so you can only choose mostly middles towards the back? Not sure why that would be any better than not being able to choose seats ahead of time at all. You choose seats ahead of time so you don't end up in the middle.
This will likely hurt elites the most. As a Gold I'll probably be getting very little benefits with basic economy tickets. So the option would be to pay more, or end up being a de facto non-elite. Doubt these will allow changes or upgrades.