Excellent work on the comparison of the PG 4 to IA 2 rules. I agree with you that most people will be coming from PG to play IA and fewer will come from IA 1 to IA 2.
I'm setting up an August 1914 scenario and your summary and comparisons above saved me the trouble of reading through the whole rules. And as you say, trying to remember during play, a cheat sheet will help greatly.