Just going to chime in, since I like to do so.
The banning, in my observation, certainly only tends to happen at a threshhold of 20+ players. Kingmaker was a tremendous example, I was trying to explain to my roommate that if cast at the appropriate time, an Arcane Nexus could theoretically garner ~1000 pearls by the time it is dispelled, so then if recast with 999 will become almost effectively undispellable, and if it IS pulling in ~500 pearls per turn, for example, then that is an absolutely staggering amount of power, that destabilizes the entire game. Ultimately I believe in the potential for destabilization, but since there is only one avenue to achieve that level of power, it is blatantly unfair to everyone who didn't take an S9 pretender.
I do think it would be best if Armageddon were disallowed as well. Unfortunately, it's anonymous, so it has to be on the honor system, or Wish removed entirely, which is a tough paradox because many nations have little access to SCs, and especially in a larger game, the uniques (elemental royalty, etc etc) will be gobbled up fast, so you really are left with Tartarians, and wished Seraphs/Chayots/etc. So removing Wish would not only interfere with the full benefit of even taking an S9 pretender, but would also lead to crippling some nations' late game strategies.