1. Remove all expansions after Wrath of the Lich King except for Warlords of Draenor and Legion.
2. Swap places of The Burning Crusade (levels 75-90) and Wrath of the Lich King (levels 60-75). Introduce Draenei and Blood Elves. Also introduce two clans of Worgen. (Alliance and Horde).
3. Remove all Battlegrounds except for Warsong Gulch. World PvP should be everywhere.
4. Release the expansion The Emerald Dream for levels 90-100. Do not introduce Pandarians. No Garrisons ever. But do introduce High Elves and Goblins as playable races.
5. Reintroduce a reworked Warlords of Draenor expansion for levels 100-110.
6. Reintroduce a reworked Legion expansion for levels 110-120.
7. Release the mini expansion The South Seas for levels 120-125. Introduce ship combat between players.
8. Release the mini expansion Into The Maelstrom for levels 125-130.
That is all that I can think of right now.