More ideas keep flooding in. I'll add these to the OP but post them seperately as they come so you don't have to re-read the first post over and over again.

Here's how I want to structure things:
- [u]nightmare session[/u]
The [s]victims[/s]dreamers find themselves in different locations of the nightmare area (which I'll provide a map of) and attempt to find one another. There will be a semi-obvious goal to "work towards" which I will not disclose just yet. 
In order to reach said goal, you have to work together. People who get killed, forcefully removed or incapacitated inside the nightmare are thrown out of it - they "wake up" early, can't help the others for the remainder of the "session" and suffer... and suffering severe damage in the nightmare will have "repercussions" in the real world. This is a crucial element of what I have in mind. There won't always be an easy solution to a problem, sometimes people [i]have[/i] to take a hit in order for the others to proceed. A "session" ends when either nobody is left, when a significant amount of time has passed or when I feel that a significant amount of progress is achieved. 

- [u]day phase[/u]
Is all about dealing with the repercussions, potentially interacting outside of the nightmare and making plans for the next nightmare phase. The length of this can vary depending on whether you choose to interact in the real world.

- [u]next nightmare phase[/u]
You will find yourself in random locations of the nightmare again, but a certain, varying amount of "changes" you've made to it will be persistent, making it easier to meet up and/or progress past the point you reached last time. Depending on [i]what[/i] you did, it could get more difficult as well.


I suppose it would make sense pointing out that the general "level" of this would be [u]between casual[/u](due to the lack of a hard ruleset)[u] and advanced[/u](due to being GMed)? I might cross-post this in the advanced IC section for this reason. Generally the way I'm envisioning this involves [u]some GM-ing[/u] on my end (parallel to the free character development/interaction between the lot of you), but since everything would go in a very [i]reactive[/i] way, writing long paragraphs doesn't always make sense(I'm not discouraging that though).