Alternatively, bag or sling a pony, so in a situation like this you could ditch all your gear and ascend using only the pony. Won't work if the pony is hard-mounted to your tanks, which is why I say bag or sling it.
Also, I would think that, as long as you had a spool of some sort along with your SMB, you could shoot the bag normally and kind of crawl up the line once it's deployed and floating (like everyone has said, you certainly wouldn't want to attach it to yourself on the way up!).
>*< Fritz
Fritz, respectfully.... Adding another piece of gear to address the shortcomings of another dosn't solve the fundamental problem....