I know you've got your plans as to how this should proceed, but I'd like to see a 2U 8-channel WITH IO Module and LED Meters.
Would it fit?
8 channels WITH IO-Module AND LED meters... probably won't fit in a 2u. Not unless I redesign the SC-1 PCB, make it longer, put the transformers on the same board, and add a daughterboard for the switches and VU.
8 channels will fit in a 2u but without IO module. LED meters may fit even at 8 channels.
Since I'm sticking 8 in a 2u, rack I thought I'd throw this in. Each SC1 is a little over 20mm high, min spacing between 8 units in a 19" rack is 48mm. This leaves you less than 28mm for the secondary unit.
(This, of course, is just for the density I like. A typical rack has a 410mm wide area for controls (say rear or external on/off). If filled, this is 51.25mm per channel. My focusrite saffire is a bit under 440mm, or 55mm per channel.
for my 8 channel. I'm about to fix the front and rear panels with labels so I'll have new photos in a day or two. Then waiting for the secondary pcbs to arrive. I'm not putting in trafos so there's plenty of room for me.)
Off spec, the low profile cinemag input Ruel used will just fit (at 27mm) but the output (at >41mm) definitely won't. The IO module will fit without them (about 22m), but it'll be a tight squeeze and may look funny (with odd offsets - small knobs are a plus here) but probably won't fit with the meter unless you're filling a wide unit (about 14-16mm, nearer 10mm if you replace the pot with resistors, hard wire the jumpers and flatten tall components). Of course, you can use the IO module and mount the trafos behind the cards.
If Ruel can get you some drill templates for the IO and LED units (and some top-bottom distances with the drill offsets) since all mine are approximate, the best is sticking it in CAD and seeing if you can get a decent looking frontplate. I'm using Solid Edge 2D, which is free, but easy to use and does multiple layers, which is good for this sort of design work.