Here's two minor must fixes that have occurred to me.
1. Create a tower guide online/a non-spoiler wiki for the game. I looked previously and couldn't even find the names of the towers and didn't have the opportunity to boot my game up. It seems like, beyond the easier reference, it would be good marketing for Siege of Centauri. A full forum on the website may also be good where people can share strategies, stories of epic matches, or write fiction based on the game. I've seen some very robust forum communities before, and in my opinion, Stardock is missing out here.
2. Place a limit on the screen shake effect when multiple Minos Cannons are firing. Get about four or five of those firing at enemies and the screen is vibrating non-stop. It makes it very difficult to do accurate tower placement.
Then this is kind of an addendum to the less-immediate and harder-to-pull off suggestions that are my old top-priority list. Tiered steps on the terrain overlooking paths. The lowest step would be toward the path and the next highest step would be behind that. This would allow more towers to have a line-of-sight on the path further back.