Either a Tech that would unlock the ability (or just a game menu) that would allow a player to compare (on a graph) different aspects of a players status.  (ie compare dust output, tech output, fleet strength, etc).

This could be implemented into an espionage idea, or just a tech that would unlock this kind of "spying", or perhaps even a ship or "Hero Type" that can be "inserted" into an opposing system to allow "spying - graph comparison".

More real time information on comparisons is missed (which is readily available in other civ type games); as a default menu option.

Idea:  https://www.games2gether.com/endless-space-2/ideas/1582-a-tech-or-in-game-menu-that-would-unlock-comparison-graphs