I don't expect him to be a dynamic force in his D-zone, he's always going to be limited by his size in tight spaces. That's part of the tradeoffs that come with his speed and agility and playmaking.
Ghost gets into trouble when he tries to do too much, that's part of learning your limitations. It's a problem for most talented young players, they're so used to dominating at lower levels they develop bad habits, and one thing they need to learn at the NHL level is the other guys are really talented, too.
It's not like he has to make major changes in his game, just cut back on dangerous turnovers, once or twice a game decide to play it safe when he doesn't have a clean entry and there's no one behind him.
You can see that with Sanheim, when the season started he was out of position too often, free lancing, trying to make things happen. Since he returned he's been more disciplined, still had a number of opportunitites to make plays, but wasn't forcing things. Over the course of a season, he'll have 3-4 chances a game to jump in, which means 250-300 opportunities over 80 games - hit on 10-15% of them and you're a 30 point ES D-man.