I understand Matthews is a really good player and would cost quite a bit to trade for, but in a highly hypothetical scenario where Toronto is trading Matthews, the team acquiring him is looking to contend for a Cup. Why would a contending team trade their 1D away? They would be looking to add Matthews to the core featuring the 1D and the rest.
Look at what Vegas traded for Eichel. Look at what Carolina and Dallas traded for Rantanen. It wouldn't be Faber going the other way. Based on those deals it probably wouldn't even be Boldy going the other way. For Pettersson, Thompson or Barzal it definitely wouldn't be Faber or Boldy going the other way.
Rossi is the best asset we have that would realistically be moved for a big time name. Kaprizov, Boldy, Faber are the core that the big time name would be added to.