I'm having my rack double as a producer's table, so the whole back side will actually open up... make it really easy
Don't think for a second I consider this "ideal". For me, this is a compromise. What I really wanted to do was use four heavy duty ball bearing drawer sliders, two per side, then slide the rails forward using a nice steel handle. However, that would have added about 2.25" of width per rack, and that would force me to have four racks instead of five. if I do the fifth rack (all the way to the left, off camera) at a 45 degree angle, I can miter off a sixth rack 45 degrees off that one, 90 degrees from the four you see in the camera. 6 * 21 isn't bad at all

I measured it earlier while bored on the phone so it will fit, if the depth isn't more than 16" instead of 22" like the others. Though all of my outboards are 6-10" deep, so thats plenty of space, actually. I could even put the ADC patch bays there. Either way, a sixth is doable.
Now I just have to figure out how to keep the wiring clean at the patchbay and board... since you'll be able to see it/walk around it.
Through the back framing, which I would think you'd have, drill two or more 1/2" holes through the width of the frame pieces, so you can insert 1/2" steel rod through the the width of the entire rack, then use velcro ties to hold the wires to the cross-rack steel rod. Or copper pipe, whatever floats your boat. Just don't use threaded rods, because you'll wear into the wire insulation. Something smooth.
And to cover the back of the racks, use cabinet doors or possibly a curtain behind each rack. When I had my pro studio a decade ago, we did the curtain thing, that was very convienent, and we had the curtain people match those curtains to the window drapes that we bordered all the interior windows with, just to make it nice looking.