If Arz doesn't want to retain salary, giving back a player in return such as John Moore and his $2.75m cap hit would be the next best option. Moore is only a 6-7 D-man on this team, and can be replaced with Vaak, Lauzon, or a $1m free agent. It would equate to much the same, at least for the next 3 seasons.
I do think OEL is a bit overrated, and overpaid. He was highly touted coming into the league, but is still a solid player and the team captain. The B's may need that leadership as Chara and Bergy ride into the sunset.