I got a splendid (IMO) idea to improve the base building minigame: The issue it currently has is that it can be played the same (optimal) way every time. Goldhawk has added adjacency bonuses etc, to spice the game up, but it doesn't generate additional variety or add that much real options gameplay wise as the only real choise the player needs to do is what buildings to build and when to do it. There's "only one" optimal way to place the facilities.
So what if each base building grid was randomly littered with 4 to 8 (depends on difficulty) debris tiles that block building any structures until you excavate it, which costs significant time and money to do. Now player needs to weight if it's worth to strive for adjacency or build faster and cheaper but with unoptimal facility placement. With this relatively simple addition, every playthrough would be different and you'd also need to build more facilities in the 2nd and 3rd bases when you can't fit everything in the first one. Currently all additional bases tend to have just radars, hangars and missile batteries as almost everything you need can be built in the first base.
Make sense to you?