I read the re_solidworks intervention that has rightly brought to light the most "difficult" points.
I do the devil's lawyer by bringing some "pessimism" on some points (not sure to break the project, on the contrary to make it grow by removing the shoots too much): I've been working on a network project for years and I've had some experience.
inclusion of nonprofessionals: I continue to be against, both for a reason of "mind approach" to the concept of "business", and for practical reasons: availability on working hours, billing mode ( occasional performance? with the limit of 5000€/year? mmm...), availability of regular licenses
tariffe: it is useless to hope to find agreements, I am for a mechanism of self-regulation. a partner becomes a "promotor of a job" that is entrusted to another partner: the second makes a price, the first invoice with a margin that covers responsibility and investment in the phase of fitting to the customer. in both cases there is the convenience to be as competitive as possible by automatically balancing the relationship.
manufacturing companies: I am against, at least at first. It would be much easier to manage a small network of complementary services, at least at first.
various cultural contributions: I sincerely appreciate and admire the technical culture of many who write on the forum, but "being on the market" is another thing (unfortunately
in summary, I would start in agility with
small numbers (10 members are already many) and
minimum investment: coordination of web visibility and brand, structure of data exchange (common server with archive, dropbox and internal forums?), software correlation (useless to have all the same cad). then if the thing takes off and grow bigger initiatives ... better!