After starting my fourth migration on nightmare I decided to write down some things I could suggest to change.
1. Bullet tower and spray tower damage per essence is week (even before including accuracy) at 5E for 4-6 damage or about 1d/e (1 damage per essence). Taking a look at bow towers which have 1-1.5d/e and much greater accuracy or Balistia towers which have a whooping 3.33-5d/e it makes neither the bullet nor spray even worth getting an elemental upgrade.
Maybe have a non-elemental upgrade for bullet and spray towers (potentially even bow towers) even if they are expensive for a small damage increase (late game building slots matter more then resources).
2. Ability to turn on an option to show doggo spawns as a message. As well as maybe an option to quick jump to nomad spawns.
3. F3 screen have ghosts have a colored tag on them to locate or ability to more easily see them, especially late game.
4. (Don't know if this is possible with the engine) Perks update when loading into a region so you don't have to deconstruct buildings whenever you get a perk for that building.
5. View quests from region.
7. Royal fountain (5x5 tiles) that costs gold bars but stores much more more water. Or a water tower.
8. Like early stated building slots matter more late game so maybe a warehouse to store basic resource: wood, stone, iron. That costs stone instead of wood like the basic storage but has a greatly increased storage value.