its been looked at before in some form or other
at first glance it seem like it couldn't possibly fail with all the mixed skills and experience but I think good engineers are artists and as such are like a herd cats, each one has its own way and be dammed everyone else
standing in a row is the last thing they want to do

I'm guessing another problem is there are easer ways to make a bob or two than building cnc machines ?

I reckon the only way to get anything like what your after is for one person to take charge of the design (like a build log) and carry all the financial and progress chasing weight and let users put bids in for the various machining jobs that need doing
its a big ask but the right person might be able to make something of it?