I'd like to see a "Worlds of D&D" sourcebook instead of just sprinting a single setting. The intro can mention that more detailed historical and geographical info can be found in various products on DMsGuild, and each setting can get its own chapter. The settings chapter can have a synopsis of...
My advice would be to make sure you have a good grasp on the perception rules—they're very flavorful but might confuse prior editioners. Also difference between perception and investigation.
I think I see what they were going for, but I wish they had flipped it around — the power would be cooler if it only worked when a fighter was ABOVE half hp. It could be described as the high level fighter no longer being threatened by the stresses of the opening rounds of combat, and that you...