@Kymberly Mohair will definitely be fine as weft for that. For warp I'm not sure. I could see it fraying and ultimately breaking as it gets pulled through the heddles and reed.

Even then, repairing broken a warp thread isn't so bad. I used to be scared of it until I had a project where I broke over a dozen warp threads before the end of the project (I allowed too much draw-in on a high-tension warp, a common cause). By the end it just became a mild annoyance.