I remember someone did the Mackie/Behringer route here and used ribbon cable under carpet to run the audio. It worked for the run lengths involved. I was skeptical regarding noise and longevity. Ribbon cable wired to TRS would not last a week in a heavily used studio.
mcminone.com has some killer prices for Behringer and Xenyx these days. I saw a 5 or 6 input 2 bus mixer for $50. With prices like that you will spend more for the wiring than the equipment.
I have installed most of the analog and digital personal mixers and can nitpick specs, sonics and performance. HEAR, AVIOM, and Furman all last well in heavily used studios. Mytek suffers from abuse because it connects with 16 pair and DL's and no one pays attention to bent pins and loose connector housings. I only saw Nemesis, the UK system?, at Power Station and it was always perfect given the tech staff all over it.
The client is the star, but I have never seen more than eight individual channels used on any of these systems with rock, classical, jazz, advertising, etc. It is usually stereo mix, multiple more ME's, and sometimes talkback. It totally beats distributed stereo cue systems, but the fewer choices the better.
DIY is cool, but there are huge diminishing marginal returns when it comes to something like a cue system.