I agree with most of your ideas (who would have thought) but one:
2. Intermediate stage: (L20-L52)
No participation in CW
Why would require an idle player (I still assume that the need/desire to play CW comes from idle
and not from classic due to the idle-focused rewards) to play a significant amount of classic until they are able to participate in what they want: CW?
I agree for ladders and CL, but not for CW. Progress in idle is already super slow. Denying newbies the most significant buffs you can get in the idle game is not helping but frustrating instead imho.
But the other ideas sound great for me!