I posted a while back and got some great feedback (Thanks Peteeng), and finally decided that the PrintNC would be the best design for me. However, after much investigation, decisions on required work area, sourcing steel tube, etc., I came to the conclusion that I don't have enough free space available for a router/mill capable of my desired 24" x 24" work area. I would prefer not to scale that design down too much as the cost does not decrease significantly, and an upgrade (scaling up) later would cost considerably more (new linear rails and ball screws, as well as additional lengths of steel tube) on top of the price of building the first machine.

The MPCNC is recommended by a lot of 3D printer enthusiasts, but I often hear that this machine is quickly outgrown and is limited by the rigidity of the plastic parts acting as structural components. I found the Solsylva design, which caught my interest since it used bearings on pipe, while using plywood for rigidity. I took aspects of this design, coupled with the MPCNC and a bit of Onefinity inspiration (I only found out about this machine after I had drafted up the design).

What am I missing with this design (picture attached)? Quick summary:

Expected material cutting capabilities: plywood, hardwood, aluminum
Red parts would be 3d printed, with plans to mill replacement pieces out of aluminum.
The wood-coloured parts are plywood (surprise!), but could also be cut out of aluminum later. The holes seen in the upright boards, where the rods appear to be held in place would actually be clearance holes, with 3D printed clamps (bolted to the plywood) to locate and attach the tubes to the plywood, as well as allow for some adjustment.
Bolts and clamps would be used for fastening as opposed to wood screws (I have plans, but I want to keep this relatively brief)
The linear 'rods' are stainless tube, with plans to use 1", 0.125" wall thickness 304 stainless
The 'bearings' are three 608 bearings arranged in equidistant triangular pattern around the tube, with six bearings total contacting each tube (three at the front, three at the back).
The planned work area is ~16"x16", with a Z of 2-3"
Spindle: 800 watt router, or 800+ watt water-cooled spindle w/vfd
Drive system: TBD, but belts or ballscrews are the current top options, dependant on the rigidity of the frame