Obligatory joke opening: Oh so you want people to write fanfiction for your fiction?
Now moving on.
I know that writing for someone else in their setting, I struggle because my writing style will probably not be the same as theirs, so it'll not fit together. Obviously, you mentioned this is what you'd want, so it is good that you recognise that people will probably write differently.
The next issue is that you don't want to write and mess up something. No matter how much you tell me about your world, there is no way you can tell me every detail and how it is in your head. This puts pressure on the writer, which might lead to them ignoring the details to avoid getting them wrong, which can mess with the writing quality. Also if they assume something and it is important, but then they find the assumption is wrong, it can really ruin the ideas they built in their heads.
Being flexible with your world is probably big here, and talking it out with the writer if they do mess up to see what can be done. Obviously this can ruin the intended vision of your project, which you don't want, so it is pretty tough to manage.
Granted, I never really wrote for someone else, so these points might not be as big as I think they are, but I wanted to mention them regardless.
Anyway, I'm fine with more experimental cyoa's as long as you, the writer, are consciously deciding to do things the way you are. Normally a highly linear story would be bad, cause of the sites namesake, but keep in mind that your story STILL has choices. Sure, it might take longer for some to take effect, and that is the risky part. I'd say that it is still fine, just make sure your writing (or the coauthors) pulls the reader in so they keep reading despite the initial part not meeting expectations.
Moving back to coauthors, I haven't looked at the google doc yet, but I'm getting the feeling that you have a pretty thought out idea, which means you are invested. Getting random's to contribute leaves a lot of room for disaster, since you'd ideally want them to be as invested as you are. I'm pretty sure you won't be paying the coauthors, which means you probably won't be getting professional level stuff, and they likely won't act very professional. People will probably prioritise other things over your story, which can make it feel like nothing is getting done.
Anyway, this obviously depends on the coauthor, so I guess you just need to make sure you find the right people. Just, personally, I'd say that even if you find someone who seems perfect, be prepared for them to give up half way through, or something. I might be biased, but I'm pretty sure there are plenty of people who lose motivation or just change priorities.
Finally, I wish you luck, and I do wonder if any people will offer to coauthor, since it is quite the undertaking, but would be pretty fun to even just look on from the sidelines.
TL;DR
Good luck figuring this out, quite the pickle if you ask me. Anyway, I'd say go for it, breaking reader expectations isn't a bad thing, it is just generally harder to do right.
EDIT P.S.
Hey I remember you posting about this (world at least) before, so you're definitely invested! Anyway, I looked through the google doc and you definitely seem to have a solid idea (of the world, and plot given the thread,) which is good.