Hello,
For this suggestion I wold like to suggest maybe adding a feature where amazing large alliance calls and storms are half the price to premium members or at least a discount. Obviously if you are going for the money these missions are worth, they are not worth 10 coins and 20 coins. Maybe add a discount for premium members. Even though you gave them a discount, because they already have premium they can take advantage of it. Maybe spending more coins than if they were at regular price because it comes with premium! It does not create more spammers because you’ll have to grind 2 levels in MC including the tutorials10 coins to only get enough for premium. Once they get premium account they will have no more coins even to start a discounted large mission. I think it’s a VERY attractive feature for starting players.