Except the part where he spent too much time in the weight room, became slower, and was more infectual as a defenseman. There needs to be a balance. You can't just spend time in the weight room if you don't know how to use that extra size proportionally. Heinola is a player he is because he plays to his strengths. He needs to continue to play to his strengths while minimising his weaknesses.
I'd just add that for those of you who watched the media availability with him and Schmidt a while back Heinola has out on a fair bit of muscle. I can't really watch the Moose these days, but in the last few where seasons I did catch his games I wouldn't have described him as a lightweight, a weakling, or even particularly small. He also has a decidedly nasty streak when riled, as Moose watchers will know.
Whether or not he has what it takes to carve out a strong career in the NHL is for sure an open question, but he isn't some shrinking violet who shies away from contact, isn't a laggard on the ice, isn't a defensive black hole and isn't notably lazy or malingering. He also isn't Niku, Vesalainen or Juolevi.
Also, he's our prospect, and it's in the team's interest that he succeeds, either so we can keep him as a part of the new core moving forward or trade him for something we need. Samberg is years older, and still makes mistakes -- and also makes great plays that suggest that patience will be rewarded with him. I expect Heinola's trajectory will be much the same, if all goes well.