I think these are some key components:
- just...having it be easy! There should be an easy way to access the project and communicate.
Trading drafts is fine, but it can be problematic as sometimes the ownership of the draft switches because of a weird bug, the other members of the collab group can't work simultaneously on the same draft, etc.
- easy communication! Some collab groups want their conversations to be private, and right now, the forum doesn't give that option. I agree with some others that PMs moderated by mods or leaders would be amazing to have. :D
And having an account for everyone to work in is a great idea, except logging in and out of your main account is a hassle (uploading drafts mainly) and you can lose progress. A pro of this method is you can leave messages for your group members in a draft within the account.
That's my opinion. :)