I believe Destiny should have a fourth character slot for players who want to make a second or third class of their choice. This would allow players to expand their gameplay by having the option to rank up another character. To prevent players from having four of the same class, a limit should be set to how many characters of the same class a player can create. Since there are three character slots currently, three would be fair. Once a player has exceeded to the maximum number of classes created, the option to create that class would be removed from the character creation menu. I've added a poll so the community itself can vote on this as well. Maybe a future implementation?