First of all, I feel like Blais could thrive on the 1st line. He's good on the forecheck, he plays a pretty physical game, and yet he's also clearly talented, and has a pretty solid shot. I think he could be a bit like Buchnevich, ironically, and provide some toughness, while still being very good offensively.
The second tweak is also one I feel could be pretty good. Goodrow has been a solid presence on the 1st line, and I think his game would free up a lot of space for Panarin and Strome, his forechecking and passing could really elevate the 2nd line, but the biggest reason for moving Goodrow to the 2nd line is to move Kakko to the 3rd line.
Putting Kakko on the 3rd line would recreate the kid line, and it should help out with his confidence. He's clearly been struggling this year, so having him in a lower pressure environment, while still having him on a talented line might be just what he needs. Plus, who wouldn't like to see him play with Chytil and Laffy.
Another candidate for a spot in the top 6 is actually Gauthier. His speed and talent makes him an exciting prospect, but he hasn't really had a real shot on the team, nor does he have a real place on the team, and I don't think he will unless there happen to be some long term injuries.
On the defense, I did swap Trouba and Lundkvist. I'm not sure about this, but I do think Lundkvist's offensive talents are kind of being wasted on the 3rd pairing, having him with MIller would elevate his game, as he'd play more with the top 6, and he could play a more offensive game. I also think Trouba is more equipped to play alongside a much less offensively dynamic defenseman, while still having the experience and defensive capability as to not hurt the defensive capabilities of the 3rd pairing. I know Trouba and Miller work well together, but I think that these pairings would be better overall. We should also stop playing Tinordi, he's kind of meh.