If you're doing metal work, you're going to want to stiffen your Z axis from the get go and get a spindle, not a router (low RPM, high torque). Probably wider plates on your Y as well. The 2020 rails WILL flex from plunging so go 2040 at minimum or find use cast corners to bolt them to your table as close to the Y rails as possible.
The 2020 holding up the X axis is only a temporary setup. Ideally I will machine some aluminium plates to replace the XL plate running along the Y axis, along with the C beam endplates on the X axis C beam (similar to the OX). Unfortunately a spindle is hard to come by - I can import one, but obviously the risk goes up as I dont know what I am getting, and the shipping cost can be huge. Even sending US$200 worth of parts to NZ costs US$70.
Most of the spindles are from china anyways. Just get one off ebay And that's not much.... I paid 90$ US to get my 1 meter rails to Canada.....
The $70US is just for plates - if I was going to get the C beams shipped here, it would cost $200US for 1 1m C beam! I will look into the spindle idea.