Strixhaven Spoilers - Mystical Archives - Japanese Alters [MTG / EDH / Magic: The Gathering] 

So much to like about these masterpiece variants, looking forward to seeing more of those. The new wording "mana value" instead of saying "converted mana cost" could be more intuitive to newer players, and taking up less space on a card is also great, CMC would work fine for long time players though you're right. Also on Demonic Tutor it now just says "shuffle" at the end instead of "shuffle your library" which is another nice change to clean up the wording of cards and shouldn't be too confusing to new players.

What cards do you want to see get the Mystical Archive treatment?