Since you are working "outside", it seems that your interest is skewed more towards handling the solid waste that comes off the machines rather than air cleaning.
It is a generality, and no doubt there will be those who disagree, but I would say that skews the solution in the direction of a shop-vac rather than a "dust collector".
A "dust collector" (be it a traditional DC, or a shop vac) is essentially an air pump. Any pumping system presents a tradeoff of what to accomplish with the energy applied to the system. It can either suck harder on a small straw (using the energy to create more static pressure), or it can suck more air through a bigger straw (using the energy to move more air). Cleaning up your shop or your driveway requires more static pressure to move big chunks with a smaller volume of faster moving air. Cleaning the air requires moving large volumes of air through a filter. It is a tradeoff…you can't get more of both without providing more energy.
As Dyson will quickly tell you…the main problem with a shop-vac for solid waste handling is…the filter clogs. With a shop-vac system, that is the main reason you want some sort of a "separator" on the front end of the system so that less of the filter-clogging residue makes it to the filter.
Since the filter on a typical shop-vac is NOT a fine-particle filter, putting a cyclone there could be considered "overkill", as the advantage a cyclone has over something simpler like a Thein baffle separator is that a cyclone removes finer particles better. With a shop-vac, those tiny 1 micron and smaller particles will just go zipping merrily through the filter and not clog it.
For solid waste handling only (no attempt to clean the air), a shop-vac with a large volume simple separator is the most efficient and cheapest solution. A metal trash can with carefully positioned "in" and "out" PVC fittings in the lid is a good separator. The "in" is just an elbow that shoots the debris in a path that will send it in a circular motion just below the top. The "out" is just a short pipe down the center about a foot long. Sounds too simple, but it works well for macroscopic-sized solid waste. Just like a cyclone or Thein setup, this is using centrifugal force to separate chunks from the air…it is just about the simplest form of that and works well enough for this purpose.
Again…the downside to this kind of a system for most people would be that it provides very little reduction in the air-borne dust. It is good only at keeping the solid waste from piling up in your work area.
