The Global Campaign would be amazing, players actively affecting the story of the Mortal Realms as it moves forward.
I agree with the variety of Gargant kits. Ever since they were hinted at in the Old World Reveal I've been talking and posting about the variety of units and how insane GW could go, most people go "Look at the Knights you'll get one or two new Kits blah blah blah" but as others have said the Knights are already available for other armies in 40K and the Gargants will be a thing all their own!!
I want Ranged Gargants with ballistae sized bows and Cannon sized handguns.
Shamans with actual trees for staffs.
Soldiers with Armour plating, Chieftans and King Brodd himself.
I want Mammoths as Mounts and Scenery Pieces
Large Cave Bears as hunting dogs, Half-Gargants that fill the role of Armigers just shorter than an Aleguzzlar.
The Aleguzzlar to become the runt of the army.
And I'd love if every Gargant was tall enough to look Archaon directly in the eye. Monstrous beasts that deserve the title of Gargant, that tower over Ghorgons and Cygors.
Last but not least, Johans extended family. A bunch of extra Human and Free Cities soldiers to decorate our bases running screaming in terror.