I like statistics and spreadsheets. (And who doesn’t?) And I would love to see one in the game.
Now in PvP mode you can see info about only one particular Citadel at the same time (like Win Rate, Attack Wins, Favored Troop, Weekly Restrictions, etc.)
It would be nice to see such info about all Citatdels together in a single table.
Q. What practical effect will it have for players?
A. Take effect of looking on the info about one Citatdel (whatever this effect is) and boost it. (For example, maybe noticing very high numbers of wins or losses on particular Citatdel will tell you something.)
And it feels so satisfying to look on all these numbers… 
+++++
This suggestion introduces zero gameplay changes. Also, all numbers to be arranged into the single table are already calculated in the game. So it’ll have mostly GUI efforts as I see it.