I remember my sprout experience. Not knowing what skills I was going to have in a dungeon was awful and having to swap out skills manually just to do FATEs was even worse. We're fortunate that the latter is gone and I think removing the former would be a great improvement for players trying to learn while leveling. As long as DPS and healing is capped to be level appropriate I don't see what kind of damage can be done.
I've seen quite a few new players go for level skips in an attempt to make classes/leveling interesting. The simplicity of lowers level really does push some players away.