So this post is allowed to stand? Aight.
Let me rephrase my response then.
Yes lines are often fluid. Coaches do try to spread the talent, and like I said, ideally they have the talent to roll a "top 9" type of lineup. But often they can not. And that is why the McLeod at one point was considered a third line. That highlights the difference between the top 6 and bottom 6 on this team.
Sure sometimes(though very rarely) Bratt will play on the 3rd line, and Mercer and Tatar too. But come playoffs Bratt is not on Boq's wing. Meier is not on Boq's wing. Those guys, like Nico and Hughes, are in the top 6, and then you shake out the rest of the lineup from there.
Perhaps in the years ahead Mercer develops and becomes our 3rd line center so as to make NJ a "top 9" type of team, but as constructed? We are a "top 6 / bottom6" style of team.