Just an arXiv with peer-review is not enough. There is a lot of room for innovation and improvement. There was quite an interesting discussion[1] about creating something in between Overleaf[2], ArXiv[3], Git, and Wikipedia, moreover with the ability to do a peer-to-peer review, discussion, and social networking. Check out the last[4] article in that series. There are a few implementations, albeit not covering all features, like Authorea[5] and MIT's PubPub[6] (it is the open source[7]). See also GitXiv[8]. See also the Publishing Reform[9] project. Moreover, there is quite an interesting initiative from DARPA, to create the scientific social network of a kind - Polyplexus[10].
There are experiments also in terms of peer reviewed open access journals that work as arxiv overlays. In mathematics we have discrete analysis [1] and sigma [2] (at least) which are quite good. Some journals started moving to a fully free open access model, e.g. JEP [3], Documenta Mathematica [4], Acta Mathematica [5] and Annales IF [6] (again at least).
I agree with @xvilka that there is lots of room for innovation and exploration, but even in the more traditional setting there is some movement coming from the smaller realities. It seems to me that the big publisher monopoly, which at least in my field is completely unjustified, is the bigger obstacle.
We plan to take a cut of the crowdfunded transactions, like Patreon or Kickstarter does. We could also show academia-relevant ads on the sidebar. We will never paywall content on our platform.
This covers a lot of what we're building at OpenReview.net. Obviously we still long way to go, but we already have some of the major AI/ML conferences using our platform to accept submissions, perform paper matching, and host peer-review forums.
[1] http://blog.jessriedel.com/2015/04/16/beyond-papers-gitwikxi...
[2] https://www.overleaf.com/
[3] https://arxiv.org/
[4] http://blog.jessriedel.com/2015/05/20/gitwikxiv-follow-up-a-...
[5] https://authorea.com/
[6] https://www.pubpub.org/
[7] https://github.com/pubpub
[8] https://medium.com/@samim/gitxiv-collaborative-open-computer...
[9] https://gitlab.com/publishing-reform/discussion
[10] https://polyplexus.com/