If you understood the point, then I don't know why you were mentioned a 4-cast card. That's not intended as snark, it's just that mentioning 4cc didn't make much sense.
I have already noted on TMD that Channel or Bloodrush are easy alternatives to the fact that Cycling creates a cantrip effect.
Regarding "can't be taxed", I was making a point that pre-existing abilities can be used to address the taxing issue. I don't think Wizards would EVER used such a phrase (today). At best, they would use "Permanents that would affect the mana costs of [CARD] have no effect." That language is wonky and unclean--modern Magic cards would never use such language.
I think that Wizards' attempt to make a bunch of creatures that hurt cantrips has been a dismal failure for the most part. Not because they are creatures, but because they don't work in a Blue Mentor Sword to Plowshares world. The only thing that has worked is tax effects, but those can get a little too powerful when there are too many of them. Maybe a tax effect in Green or Black that only increases the cost of instants and sorceries would have an impact.
Or otherwise making a Green or Black card that really put it to the Blue engine would hurt Blue while not pumping up Shops, PO decks, or White Eldrazi. It's just a thought.
Regarding Misstep, it annoys me to no end that the vast majority of design mistakes made by Wizards are so frequently in blue. And in Vintage you can just augment as needed for other colored spells because of dual lands.