One problem I can think of with adding an easy mode is that it might compromise the value of the game. Someone who's good at video games decides to put it on easy mode and beat the game in 2 hours. He'll probably be disappointed in the end and ask for a refund.

And before you say "oh it's his fault for putting it on easy mode!" or whatever, I just want to point out that 1) kids are stupid and they will 100% do this 2) I have a friend who plays COD almost exclusively, so he's used to putting games on the lowest difficulty and still experiencing everything so if he ever decides to buy this game (and he wants to)... yeah, and 3) humans are hardwired to always take the path of least resistance, so I'm sure there will be plenty of people who will see this as just another video game and try to get it over with as soon as possible instead of striving for perfection like the game is demanding right now.

Those are my only concerns, but I should add that I am all for more accessibility options, just not at the expense of the larger/focused/current playerbase.