I think that this mode makes a lot of sense and is a necessary change. This is how any strategy and/or card game should play out. Rather than being able to play all your cards and your full strategy at the start of the game and reaching full power, you need to gradually build up your arsenal and work up to a point where you can unleash your powerful combos.
It will initially feel like something has been taken away, but the result is that you will have to work harder and think more strategically about how the game will play out, which is really what we want from a strategy game. It should be more satisfying to reach the point where you can play your powerful combos. Is it slow? Sure, but it is the “slowest real-time game you’ve ever played”!
I don’t think that the starting positions should necessarily have more towns (not just because I’ll have to re-do ALL THE MAPS haha), but I think this could be an interesting difference between Normal and Nightmare difficulty modes - start with 3, 2, or 1 towns - so effectively you have less of a head start and the zombies have more.
I’m currently playing as the Dwarves and I don’t think it’s making that much difference in practice. Sure, I would have played more Cannons and smashed all the zombies, but that would have made it really easy. For some races, I didn’t even need to claim towns before, but now expansion will become a lot more important, particularly early game. I also initially forgot that you can even build units.
This way we can keep the awesomely dominating card-combos, because you will have to work hard to get all the cards down and be able to pull them off, not just start the game, smack down all the cards, and wham game over for everyone!