The finished product may or may not have this but if not a feature that would be useful would be some icon or signal on the starbases to indicate they are still subject to upgrade.
When you build a lot of starbases it becomes confusing remembering which ones still have upgrades possible.
Just a little thingy like the hammer icon on the planets that would go dark when a starbase is fully loaded and come back on when new tech makes more modules available.