I have spotted some easy to implement improvements after 1k hours and 4k spm base under way:
Q functionality is missing when cursor is on an empty tile. I'd like it to select previously Q selected building.
Ctrl cvz are amazing features! But when you furiously spam Ctrl z, you might accidentally delete power pole or inserted somewhere far away. I'd like to have Ctrl shift z to undo undo, just to make sure I didn't accidentally deconstructed something.
Might be hard to implement: Modules blueprint features to remove modules, change modules and insert modules.
Having redo was on my radar for quite some time, but it didn't get through the filters that enabled us to actually finish the game before we get old :) Maybe some day later.