Here's one that recently came to me: When you're placing buildings that cover two blocks, you should have the option to choose whether you want to place them horizontally or vertically. I was recently doing some base building, and I was a little annoyed that I technically still had plenty of space for a certain building, but I couldn't actually build it because the two blocks were oriented north-south, not east-west.
Again, as with most of my suggestions, it's not a critical thing, just a small change I'm sure a lot of people would appreciate.