Okay, allow me to state it again:

Using unsupported shaft in this machine will be a waste of money and effort!
Building this thing in steel allows it to be a good performer, using unsupported shafts will allow flex, making the results no better then the same thing built of plywood.

Then two general remarks on the design:

1: It seems to me that you will not be able to assemble this thing, as the nuts will be falling out all the time.
2: If you add tabs+rectangular holes here and there to position parts, you can probably glue the thing together, if you choose the right kind of epoxy.
If not using epoxy you can still use an occasional spot weld to fix a tab in its hole.