How about this:

Game 3 ships with all races from the First two games, vanillla and dlc, with updates for all races that haven’t gotten any yet, including Wood elves, Beastmen, Norsca and Chaos Warriors. The game ships with the entire finished Mortal Empires map, including the Darklands and full Lustria, Southlands and Naggaroth. New races in the box are Daemons of Chaos and Ogre Kingdoms, with a Vortex-like campaign set in the Darklands, involving relevant other races. Chaos Dwarves, Kislev and Dogs of War added as DLC later. The two shorter campaigns from 1 and 2 are also included as options with Mortal Empires being more of a sandbox campaign with no Endtimes invasion.

It would stop sales of the 1 and 2, so they probably won’t do it, but it would get around the problem, that they’ve used 85-90% of the well-described lore and map in the first two games.