I got some ideas, maybe you find some of these useful.

Combat Simulator:

One could give the user the possibility to take over his own troops for the combat simulator at the push of a button.

This would have multiple uses:

You can test if a defensive is good enough to fend off a potential attacker without having to transfer the values by hand.

You can see what the defensive is susceptible to. (testing is much more comfortable then)

On the alliance page, there is a list of actions going on for each user. maybe we could add some kind of accordeon menu, so the user has the possibility to blank out unwanted information. Or simply ad these to another page. It might not feel as untidy as it does right now.

Galaxy:

When you actually send a fleet to a specific planet/moon, you might want to see that in galaxy view aswell. Maybe add an icon that you are attacking a planet / trading to this place and so on...

Changing Planets in fleet menu:

Imagine you are browsing in galaxy and want to attack a planet. Now you click attack. Now you realiste that you unintentionally have selected the false planet. All you can do now is change the planet and after you did that, the information which planet you wanted to attack is lost.

Changing Planets while browsing galaxy:

By changing the planet while browsing the galaxy, you are loosing the state of last "galaxy system" you where looking at.

Thats all improvements I can think of. Let me know what you think about it