It won't effect the game being an optional choice but it will bring lot of creativity to the game.
Prepare Carefully needs to be in the vanilla game in combination with Backstories mod that allows you to customize your own backstories
Combine this with Scenario Editor and imagine what great Scenarios we could have in the Steam Workshop
Current Scenario system is limited, we should be able to customize more including what type of characters we would like to start with
I see this as a large benefit to the game
creating your own backstories would step on the toes of ALL of the people who helped start up this game and all of the people who specifically PAID extra to create a backstory for the game. As a mod, there is little that can be done to mitigate it, but added to the main, vanilla game, it would be a kick in the teeth to all the biggest supporters of the game.