I reckon it would be pretty useful. It could have a variety of tools, and could possibly have the forums build in. The website on mobile is a bit buggy so this could help heaps.
There is a Discourse app you can use to access the forums. However from what I can tell it is simply a web wrapper.
A standalone community hub app for Age of Empires would be awesome, I agree. I have experimented with this a little bit. Back when most social media channels had public RSS feeds it was easy to create an app.