This post: How to increase air density on a planet? explains most of the problems I have been having, and fixes them. My current problem is as follows: On a planet with an air composed of (roughly)
21% Oxygen 39% Nitrogen 39% Krypton + the required C02
The density will be higher to allow hydrogen and helium to be more effective as lifting gases (my goal). I am assuming wind is enough to mix the krypton and oxygen in most places, if this isn't the case, please do point it out. Additionally; humans will need to have evolved filters to prevent the annoying side effects of breathing krypton (death through suffocation as a result of oxygen displacement, and an excessively low voice). I understand that lower parts of land, or places with not enough wind to mix oxygen and krypton will be uninhabitable. Also understand that as the aircraft ascend, the air will more and more be composed of oxygen and less krypton, leading to lower density and less effective lifting power.
My questions: would the increase in proportional oxygen as heights increase prevent the effects of hypoxia because the partial pressure would remain more similar?
I am flexible on the specific amounts, and open to the inclusion of xenon or argon also. The density of the above atmosphere (according to my inexpert calculations) would lead to helium being almost twice as effective. This is the goal, if it can be pushed higher I would like that also, though I know nitrogen is important for plants.
Would this composition require a different atmospheric pressure?
I also want to know if there are any other problems to deal with.