Right now I think he would slot in as the 1c. I'm not sure how they're going to do lines but Asplund - Mittelstadt - Thompson would get eaten alive by most top lines in the NHL.
Likely yes, and this probably isn't the best thread for the comment, but all of these posts where people list the Sabres roster and talk about how bad it is don't take into account that the players are actually getting better. Who they were last season, or three seasons ago, is most likely not going to be who they are next season.
That said, is ATM a number one line right now? No, it's not. But my hope is that an ATM line, with, say, Bjork - Cozens- VO on another line, and Skinner - Vinnie - X on another line causes some interesting matchups, especially if Donny rolls the lines. Scoring by committee could be really fun to watch this year, because there's no #1 line, and any of the lines could theoretically be the top line that night.