How about adding a Map Size preference ladder like:
I had the idea because I want to play ladder, but I didn't feel like playing a small map. (because being low rank, my map pool is always little maps )
It has to be a multiselect (like factions).
It chooses the preference if all players want the same.
This is important for balance to avoid players specializing in concrete map sizes
player 1 wants 10x10
player 2 wants 10x10 or 5x5
then 10x10 is chosen
player 1 wants 20x20
player2 wants 5x5
random size is chosen
You can also choose none or all maps sizes, and it's just random/choose the other player preference then.
What do you think?