I don't know what this is accomplishing. Moving Swayman for a broken Demko is a rebuild move and adding Miller is a win now move.
The simplicity (if the NMCs can be worked out so maybe not so simple) of Elias Lindhom with a million bucks in retention for JT Miller is appealing. Lindholm slides into #2C in Vancouver and at 6.75 can be fine at 3C if Vancouver can upgrade over the next few years.
For Boston
Marchand Miller ???
Geekie Zacha Pasta
Frederic ??? ???
And fill in with Coyle, Poitras, Lysell, Merkulov, Brazeau depending on the chemistry. You probably want to move Carlo out to a team like Buffalo or Ottawa that is young forward rich but really could use a defensive minded RD to balance out the top 4 pairings.