It's a good idea. And I actually considered something like that. It would be easy enough to do, but Ilmy reason against it in this one was pedantry -- I knew readers would have a habit of writing lines that were just things happening, rather than actual choices from the main character. By writing the lines myself I could make sure people were presented with three actual decisions they could make to influence the next part of the story - instead of them narrating random acts of god. But this isn't necessarily a bad thing, it just makes it less of a "choose your adventure" and turns it into a "help me write this story".
I think I'll try it that way next time, anyway. And why stick at the first three? Might as well make it so anybody can write a line suggestion, and it's the one with the most votes by next day that gets used.
Regarding deaths, I guess I could just pick a number from 1-10 in advance. Whichever person comments, say, fourth -- if that's the number I pick -- is unknowingly writing the fatal option. If I pick six, and only five people comment, well then you're definitely safe.