You wrote some time ago, and are still watching this thread, so I thought I'd respond here too, since I've had some experience in this area,
1. Why did you leave? What influenced you etc.?
Generally, because in each case I felt that I had learned everything I needed to learn where I was, and there was no longer any learning benefit left.
2. What was the hardest step you had to take to leave?
Gathering my own personal resources up to the point where I could confidently confront the cult leader in each case, anticipating his or her various ploys to keep me in the cult, so that I could be sure that I could counter these with my own legitimate answers.
3. What was the hardest thing to get over? Or something you are still trying to get over?
In the two cults that took some time to recover from, the hardest thing to get over was the fear that some of my needs might still somehow be able to be met by the types of things that went on in these cults.
4. Would you have gone to a shelter if needed?
If I had known in any of the cases that there were a shelter that was staffed by former members of any of the cults that I was in the process of exiting from, and if I had found this staff to be non-threatening, yes. Otherwise, no.
5. Did you think about or want help when you left?
Yes, however upon consideration of the help available, I opted against it. As I mentioned above, the only type of help that I might have accepted would have been from other former cultists of the same cults I was exiting.
6. Have you or do you think about getting help now?
Once I had properly rid myself of any notion that there was anything at all of any value whatsoever left for me in any of the former cults that I participated in, I no longer felt I needed any help and became much more effective in my career and other aspects of my life.
7. What has helped you overcome the most since you have left?
My inner work, working to explore exactly what inner psychological perceived needs caused me to join such organizations in the first place, has enabled me to recover the most.
8. If you have ever left and gone back why did you go back?
Of the three cults that I have participated in, I returned to one of them once in a peripheral manner, only to leave after I believe I completed the learning that I needed to learn. This was the cult that I was born into. I believe that this one cult may have required extra work because it was so much a part of me on even subconscious levels that it required more work to free myself from it. The other two cults I never returned to.
9. If you joined a cult why did you join? What appealed to you most?
The first cult I joined by birth, so I cannot say. The second cult I joined in order to escape the first cult. The third cult, at the time that I joined it, I told myself that I joined it because that was God’s will for me. Later I realized that I also joined it because it also suited some of what I may have somehow felt were some of my psychological needs in my life at the time that I joined it.
It seems to me that your idea about getting newly exiting cultists together with older former cultists of the same or very similar cults is excellent. I also agree with some of the other posters here that there is too much variation between most cults for an exiting cultist to benefit very much from the help of former members from widely dissimilar cults, especially to the point where a "shelter" type of arrangement would normally do much good for such exiting cultists.
I would bet that anyone who has done any real exit counseling would support the idea that in order for a specific exit counseling to be very helpful, the counselor would have to minimally have done significant research into the exact types of cult dynamics employed by the cult in question, and optimally would have specifically done in depth research into the specific cult in question.
I believe that your idea of trying to start such a shelter, that would try to focus specifically on exiting cultists from identical, or near identical circumstances is excellent, and most likely to be found to be helpful.