If you only match winners with winners there are still lots of possible unfair matchups.
Weak winner against strong winner for example.
In chess they are using the elo eystem. This means all newcomers are given, based on their first 10 games or so, a raiting. Now when they play if they win the gain points ( more against a stronger player ), if they loose they loose points ( more against a weaker player ) and so you have a sytem for ranking players and pairing players.
To a certain extent this could work in AW too. I dont know how the Cups System in E&P works but it seems to be similar. ( Maybe simpler )
The elo system is purely perfrormance based which means if an alliance changes ( stronger or weaker ) it might take some time for the new raiting to stabilize on ist new correct value.
I read somewhere that sm whant to implement it in the game but since I am not a programmer I have no idea about how, when or if it is even a good idea to use it.
Like always we will have to wait and see.