There really aren't any great, realistic RHD targets. The best vets on bad teams are Karlsson, Burns, Doughty, Weber and Petry, but those teams probably won't actually move those guys. Same goes for players like Spurgeon, Ellis, Pesce, Manson etc. whose names are out there. So you are probably paying a high price to take a chance on a young dman like Severson, Dumba being good, or an ok vet that isn't really a top pair D like Savard, Larsson, Vatanen etc. Unless you find a gem lower in someone's lineup/outside the NHL.
Pietrangelo making it to UFA is probably the best, realistic option. Other than that maybe taking a chance on Subban.
They should save the cap space to take a run and Pietro and failing that just move Rielly to the right side.
Sandin-Rielly
Muzzin-Holl
Dermott-Lilly