You are assuming that the private schools have (or will have) some sort of all-encompassing, statewide infrastructure in which they can make the decisions/classifications that you claim they can make. Even if that were the case, I dont think the IHSA would agree with any other grouping of schools telling the IHSA where certain schools should be classified in the IHSA playoffs. In addition, if St. Rita is too small to be in 8A, do you think those other schools you mentioned would volunteer to bump themselves up or would agree to being bumped up in the IHSA playofffs by some yet-to-be-formed overarching private school group? I think you have made some pretty big assumptions here in the name of expediency.
I agree, but your alternative is to include Rita with the likes of LWE, MS and HF in the 8A playofffs, assuming they can get past Loyola, Marist, Rice, MC, etc. in their own district playoffs. You've corrected a wrong with another wrong. The fact that Rita has been in a conference with Loyola, Rice, MC, etc. is different from where they belong in the IHSA playoffs. Right now, they are only 160 students away from being a multiplied 6A program.
Boylan is similar to Rita. Simply because they are in a traditionally 7A conference (and experiencing very mixed results in recent years) does not mean that they would prefer to be (or belong) in the 7A playoffs. Heck, Boylan couldn't make it past the quarters of 5A this year (their best playoff success since 2013). What makes you think they would prefer to be in 7A?
You may be correct that many private schools prefer to play each other in the regular season (although you can't include IC and Mac in that generalization since both just recently joined a conference with public schools), but that does not mean that they are willing to play up a class or two in the playoffs as the price they have to pay to play each other in the regular season
Again, I'm amazed at the amount of work you have put into this, but I think you have made some pretty big assumptions when it comes to the playoff classification of private schools.