Castellan, you say you'd like to continue the story... what option do YOU think would best allow you to do that? I'd be fine with more or less any of the above options. Some thoughts though:
1) Is a good option, but you'd still need to be prepared to post most of the time (otherwise you're not really the Battle Master anymore). An assiting back-up BM should only occasionally need to step in to pick up the slack and keep the entertainment flowing, they ideally shouldn't have to initiate major plot-progressing events. I'd tend to go with this option if you think having an altenate Battle Master would help to keep you motivated to post too, but I don't recommend it if you think you'll end up falling back on them more often than you post yourself.
2) Theoretically this would be the ideal option, except (as others have pointed out) I don't think good intentions alone are enough. Only pick this option if you're really committed, really certain that you will do it, and really have the time. Personally I don't think I'd pick this.
3) You don't have to end the Battle for someone to start/suggest another one. Unless you really want to end it, because you're sure you'll never continue/resume it, I wouldn't go with this.
4) A good option if you're not interested in Misthaven anymore. In these early days, I think you're the only person who knows Misthaven well enough to spearhead it. If you're not interested, it's not going to work. But at least this way you leave open the possibility of returning to it in the future.
5) I don't think this is a good option (see above).
So basically, I think if you genuinely want to continue the story, and think working together with someone else on it might help both in keeping you motivated and keeping the story going, Option 1 is the best.
If you don't think that having another host will help you, but you ARE committed to finishing and are sure you can do it, I'd go for Option 2... but you'd have to be really sure and determined.
If you think you'll never ever finish Misthaven, I'd go with Option 3. On the other hand, if you think you might finish it at some point, but don't feel confident you can do it now, I'd go with Option 4.
So: what do you think, Castellan?