They should bring one or two players to camp on D, even if they aren't ideal fits. There needs to be competition for those spots.
As of now, Kleven, JBD, and Guennette are fighting for two roster spots since Hamonic is guaranteed one due to his NMC. If it turns out Hamonic isn't ready for the start of training camp, each of those three are nearly guaranteed an NHL spot.
I suppose that you can argue a few players like Matinpalo, or Davies might be fighting for those spots, but I don't think they realistically are in the conversation unless there are injuries. They seem to be AHL hires.