I'm thinking that Eichel is done with Buffalo and they should retool moving forward.

Potential Destinations that make sense capwise

Anaheim

Potential Return Base:
Drysdale (to play with Dahlin Long-Term)
Henrique (Replacement level C)
Jones/Terry/Lundestrom
1st 2022
Additional pieces


Nashville

Potential Return Base:
Ryan Johansen/Matt Duchene
Mathias Ekholm/Dante Fabbri
Philip Tomasino
2022 1st
Additional Pieces


Ottawa

Potential Return Base:
Derek Stepan
Brannstrom/Jake Sanderson/Jacob Bernard Docker
Batherson/Formenton
2021 1st (Top 5 protect)
2022 1st (Top 10 protect)
Additional Pieces


These are just base returns that I could think of off the top of my head that also made sense capwise between all of the parties.
(I know Eichel is an elite player, but I'm North of the Border, so I don't know how elite he is, so don't flame me too hard in the comments )