Yeah afraid of change is good (don't be afraid of making the main character not perfect either).
Also would a trainer have to have knowledge about evolution to not want their pokemon to evolve?
Though it does look like it is an internal battle with the pokemon too (as per the anime), that is to say, Ash's Pokemon would probably know that it is up to them to evolve.
It is some kind of battle too. You see, his Pokemon will notice when they are ready for the evolution and the next stage, but Jack wont allow them to evolve causing some, lets call misbehavior. There comes the character development in the play as I don't intend to give him more than three or four Pokemon.
About the main character, Jack will not be a typical kind of protagonist. When he gets into some serious situations or trouble he runs. He runs from from changes and problems, when its time to confront to someone, that is his policy of running. But as he travels through through Johto he learns more about his Pokemon and learns too that change can be good sometimes. He also gains more confidence but starts getting more stubborn getting his Pokemon friends in serious troubles.