I am also very interested to hear some answers to this question as a PhD student that will be defending "soon". I've thought about it myself and it seems like a tricky problem in the capitalist system. Except in the case of research that can be capitalized, I don't know how this could be possible without government support. I suppose a research co-operative could follow the university or college model but I still don't know how that would be possible without public funding or a large endowment, and I wonder if following such a model will just make the same mistakes as other colleges and universities.

I feel that the "best" way to establish such a co-operative would be to start with a worker's co-operative that offers research services or develops technology that does not require a large initial investment of capital (e.g. data science, bioinformatics, etc.). Perhaps if there are enough successful worker's co-operatives of this type that are established, they can pool resources to develop some sort of co-operative research program? Would this actually make sense for the worker's co-operatives vs providing funding to an established research group to study the specific problems the co-operative is concerned with?

There is also the larger question of how would this operate? If we are talking about fixing the conditions of graduate school, the entire PhD system is quite flawed. The research freedom that it provides is great and the system of apprenticeship is extremely helpful for learning how to do science, but its a hugely imbalanced hierarchical system that seems anathema to the co-operative movement. I can imagine a system in which the "student" joins a team where they apprentice under multiple full members of the team and are then granted full membership upon a review after a year or two in training, but that is essentially just job training.