I think no levelling up and no XP is just an in demo thing and I will believe that until proven wrong
As for the control of other characters, according to OPM UK's article they are still working on it (I think) but it won't be XII's gambit system
Anyway, why is a lack of party control so bad, Star Ocean 3 certainly gave you little or no control over the rest of your party, nor did Kingdom Hearts. And I for one liked the gambit system