On any given day, the chances of success for a startup are tiny, infinitesimal even, but I think this co-op idea could actually be viable.

It needs, however, to add something else to the mix other than just an easily readable manifesto. It needs to have a portfolio, and it needs to offer governance and evidence of good financial and operational conduct, which is what corps look for when assessing risk and on-boarding a new specialist supplier.

The fact that you are only looking for developers makes me think there is much you haven't thought about yet :-)