Make the 2005 Worlds Format
I know you're planning to make things in the order you're planning, but the 2005 format was just so much fun, skill-based, and versatile (Off the top of my head I can think of 8 decks that were highly played that format). That was probably the format that had the overall best design. And you would only have to add four sets to make it. I'm sure everyone would enjoy it.