I have a suggestion that could make alliances very helpful as well.
Perhaps a give fleet option? You could research it in the diplomacy tech tree.
Here is what It might do-
You can create a fleet, then under tactics management. Click on something that says "Give Ally... (allies names) fleet." then select for how long. That would make the ally you chose have control of that fleet for however long you told it to give them control. They couldn't research things for the fleet but could just control it for small amounts of time at your permission.
This idea is kind of still exactly that... an Idea. So tell me what you think