Fortunately I don't need to have all the answers in my imaginary journal. I imagine it more as a cooperative enterprise among scientists who have become disenchanted with established academic paradigms and are looking to do the research and experimentation in that zone which is of interest to scientists themselves but not necessarily supported by the need to publish in the areas most emphasized by the academic establishment. This is not anything against what exists and what is being produced which I personally consider to be important, only to provide additional avenues to serve science in ways it's not currently being served.

You're right that credentials in this model are fuzzy. At least at the beginning it would be composed exclusively of scientists already working in their field who would want something like this. It could be possible that these scientists answering only to their immediate guerilla journal peers may see fit to support the research of an individual with no doctorate but who has demonstrated their self-education has made them capable of designing an experiment which can be quantified, criticized, and re-produced. Whether this standard would be agreed upon by the greater community would certainly be controversial with plenty of politics involved, but that reality it outside of the scope of my daydream.

As for the sustainability, it's as in question as any open source project. It lives and dies based on peoples' desire to do it only because they want to do it and others want to support them doing it. This couldn't be a career alternative to academia because making it into a business or non-profit would defeat the purpose as it would attain the same vulnerabilities to a much more severe degree than the much larger and stable existing model.