A lot of people would like that. The counter argument is usually that people shouldn't be able to disable all the hard songs to get around some of the difficulty. I don't see the harm in having a limited ability to block songs from being used in mystery or random setlists. Say 5 songs or so.
Yeah, the final tier of RB2 is pretty much a massive bitch to me on anything besides vocals. Even on Hard. I could at least muddle through the final tier of RB1 most of the time well enough.
I wouldn't care, except that they removed the option to grind through songs as in the first game.
So if they really want this to be a "casual" experience then why not go all the way? It's just a pain that the only way to make money in the game is also not fun for me to play.