Son, well, is a rather strange map. It is like Arnhem, but, there are minor differences. For example:
The Germans control Son, and have to react againt British attacks, this is unlike Arnhem, where it's the other way around where the British defend.
The Germans have to defend the Son bridge for 5 minutes, once 5 minutes has passed, the Germans now spawn 2 extra Panzer IV's.
The British have 5 minutes to suprise attack the Germans across the river, once they cross the river, the Germans must wait out their remaining 5 minutes for replacments tanks to respawn. The British only have 5 minutes to take a bridgehead over the river into Son or else the Germans will have an extra 2 tanks added on to their default spawn tank, meaning it's 3 panzers vs. no shermans. If the British manage to take a bridgehead, they get a 30 second M10 spawn. Meaning that taking the bridgehead is vital to their success.
In unrelated news, I will add ingame screenshots of finished Oosterbeek and Arnhem. Screenshots from the editor of Son and Operation Market will be added in due time.