I don't know if you want to invest in a top 4 defenseman, since that's 3-4 million (see Chiarot-Kulikov), and you have Heinola and Samberg both in the fight. De-Melo is the one you need for RH depth. I'd like to bring back a Beaulieu/Sbisa to be the PK leader, Sbisa can play top 4 too, if needed. Poolman is looking good on a 3rd pairing, and has Kovacevic behind him, who might be ready next year. The left side is more uncertain with Samberg, Heinola, Chisholm, Stanley all on ELCs, and with about 8 NHL games between them. Dahlstrom is signed, and he's probably #7/8, with Niku being pretty uncertain, as to where he fits (could he become a forward?).
We are also going to need someone that meets the expansion draft requirements. I am ok paying juat cash for say Dillion and having him as an attractive option for Seattle next offseason.
They take him and we keep our forward depth and meanwhile Samberg/Heinola get another year of seasoning under them.