One word of advice, if you have never played goalie before, don't critique a goalie's style of play. Hartzell NEEDS to be a butterfly goalie. He has the tools and size to one day become a legit butterfly goalie. If you make him turn into a hybrid, it will only hurt. That is exactly what happened to Fleury. He was an elite butterfly goalie, then the Pens changed him into a hybrid mess.
After the prospect camp in 2012, I talked to Matt Murray about what the Pens do to their goalies (we both work with goalie coach Sean Moloney, and just happened to be scheduled together). He talked about the stupid things that Meloche and the Pens tried to make him do. Basically, long story short is that Meloche tries to make goalies play like Brodeur, because that is how he played. Other than Brodeur, those goalies don't succeed in today's NHL anymore.
In today's NHL, there are 2 successful types of goalies (both of which are branches of butterfly goalies), blocking goalies like Lundqvist and reacting goalies like Quick. The most successful goalies play to their strengths. Fleury had the skills to be an elite reacting goalie, but the Pens decided it would be better for him to be a blocking goalie, which really hurt any chances of him becoming an elite goalie. If the Pens would have focused on improving his strengths from the very start, instead of making him become a more well-rounded goalie, he would be much more successful today.
The Pens need to shape Hartzell into a style similar to Rinne's, not change him into a goalie with Brodeur's style. Changing him into a hybrid between a standup and a butterfly goalie would be incredibly stupid. That would ruin him.