I think in the case of CRAU characters they would have the option of either going back to the previous reality (previous game) or to their home reality. Like you suggested, though, it would be almost prohibitively difficult to get back to their original reality, since they would have to navigate back through the CRAU reality to where they originally came from, so while possible it would be bordering on impossible. That would allow it to be case-by-case depending on what CRAU players would like on an individual basis.