Wow, this is really well made! Impressive. Bookmarked 
I started creating something similar for AoEIII, but didnāt get far before I lost motivation.
As a suggestion, one of the ideas I wanted to implement was an āunit simulatorā for lack of a better name for it.
The ability to do a type of side by side compare of for example Delhi Sultanateās Pikemen vs HREās Pikemen, and the ability to add and remove upgrades to each unit. The point of it being to better spot which unit each faction is stronger or weaker with.
As it is now, you can sort of do that in your tool as it is by opening a seperate tab for each unit 