Because we already know that Cole can see and hear dead people, do you suppose he could smell them as well?

I hope he wouldn't be able to. That would just be too much and ruin his olfactory sense permanently. I mean, he's stressed enough walking around with ghosts attacking him day after day, you'd think whoever was in charge of displaying him with the curse/ability to help the dead would go easy on him. Making him smell the dead would be too cruel and there is no distraction from that smell so while ghosts are clobbering him he would still be able to smell them and rotted flesh is not a nice scent it's one of the few times that being beaten won't distract you from the smell. Once you smell a dead body, death, decay it never leaves you. You won't even be able to ever use your own nose again properly. He wouldn't have ever again be able to smell any kind of smell ever, not roses or gardens, not the light scent of a cake baking in the oven or the heavy scent of a cigarette. I noticed that when he's with Malcolm he doesn't seem to be making a face of any sort or implying that Malcolm smells bad, but Malcolm has been dead for a few months, five, eight months maybe give or take obviously Malcolm wouldn't smell so good by this point.