I came up with some more ideas of Mal during a terrible bout of insomnia last night, so I'll share that below. But definitely Jack should be a friend to him.
Martha is going to have a for sure friends-with-benefits agreement with Gaeta. As much as I'd love for her and Jack to have something similar, I have a feeling that she's going to feel uncomfortable ever sleeping with Jack, which is a shame because they'd be really good together. Let me think on it more. I had more thoughts about her too. It was like I needed to post some wishy washy stuff before the ideas really started flowing.