I like the idea of a brand new battle system, but I'm pretty disappointed in the lack of multiple characters in a main FF entry. That's one of the things that turned me off of Lightning Returns.

In a MMO or game like Mass Effect, it's different because you are creating the character's look, abilities, and personality from scratch. YOU are the hero rather than playing the hero character. I have to assume you will have a lot of control over Noctis's abilities but I doubt you'd get much control over the rest of him. So the success of FFXV will really come down to if Noctis is a good character or not; you're stuck with him either way. It's a big risk for SE.

Hoepfully Noctis is a more dynamic character than Lightning.