[frenchyatwork]

I'm curious what would happen if a new paper tried to reference previous papers published in ArXiv instead of the traditional publishers. From a strictly academic perspective, I can't think of any reason why this would be a problem, apart from the existential problem it causes for traditional publishers.

[improbable22]

Citing papers which aren't yet published by their arxiv numbers is routine. (And, before 1991, people did the same using the author's institute's preprint numbers.) If they have appeared in a journal by the time yours is accepted by a journal, then you should add the journal info too. (Although many journals now allow you to leave the arxiv numbers as an additional part of each reference.)