i've never played a shining force,but how you described it,it would seem you're switching between roles. so that'd make sense...but still annoying.
in wild arms they sort of munipulated the system. rudy,the supposed main character,said only 2 lines in the whole game,but at key moments. so i guess they wanted you to be saying that...i dunno...but things are different now. even "you" are force to say things.