CNC Router Design: Custom Gantry Plates vs Standard Plates Plus Extrusion

Browsing through the designs here and elsewhere (OX, shapeoko, CNC router parts, etc.) there seems to be a basic commonality to all of them: the use of custom gantry plates. The plates have various holes for mounting wheels, motors, linear guide, and usually a pattern of holes for mounting the tapped holes of extrusion for the cross beam.

I've been toying with a couple of design ideas that use just 'standard' gantry plates instead. One or two C-Beam gantry plates attached to 20x40...

CNC Router Design: Custom Gantry Plates vs Standard Plates Plus Extrusion