thank you for this great on point piece. I held off upgrading from 10.6.8 until last week for this very reason. Finally mac mail just stopped working and I could easily solve it, plus needed to go to larger disk space so took the El Cap Challenge.
Honestly its nice to play around with a new OS version, but yes mission control dreadful after the PERFECT expose spaces. I will check out the solution below and come back to this thread with any comments.