I'm still interested, just working out the finer details of my character. Some things aren't coming to me like they used to.
In terms of the ghost idea, I like it. It gives players the option of still being involved, even if it's a less active role after their death. I may or may not use it, depending on how much I've grown attached to my character and if she still has something to contribute.
I can't say for certain which method of elimination I prefer mainly because of the whole 'we don't know how many are playing yet' thing. If we end up getting a lot of people, the story could be subject to dragging along due to the sheer number of posts, especially if everyone really gets into their characters and lots of stuff happens. So in that case, the murderer taking people out as we go might work out. I'd like to see what the others think as well.
The points you bring up in the missing tag and the CS' look okay to me. No objections or issues at this point.