It might be a very small step. Visual if nothing. It certainly won't improve the atmosphere. But, I want City to ban half and half scarfs inside the Etihad next season.
When you come to watch City, you support City, not the opposing team, wearing their colours on your scarf.
Not only that, buying half and half scarfs from the souvenir hawkers outside the Etihad is taking money from the club, whilst the fans are facing increased season ticket and match day ticket price increases season after season.
The name Manchester City Football Club is owned by the club, and I would assume copy righted, so City, the City Council, and their trading standards department can confiscate fake City merch outside the ground. Chelsea are in the process of doing that legally.
By all means wear a scarf inside the ground, but wear a City scarf, not a half and half scarf.