Looking further down, it used to be that finishing bottom of the football league didn't normally cause you to fall out of it. There wasn't much movement between the football league and the northern/southern/conference leagues. Maybe the problem today is that there is too much promotion and relegation to/from the Prem when we know that clubs bouncing around have huge problems managing finances.
What about just one up/down automatically and the second place determined by play/off?
I don't know the answer to this but it would be interesting to know the average length of stay in the Prem by teams being promoted in the first, second and play-off positions.