I came across the RAIJINTEK Styx Alu Micro-ATX case. It needs some mod work done for ventilation but seems like a really nice MATX case that has 5 expansion slots like the Cerberus. Its a little bigger but that allows you to fit a crazy big CPU cooler.
I say make the frame with mounting hardware and let ppl order their own TG and screens (maybe have adapters for smaller screens; I have a retina IPad mod'd which is about 10inches using displayport and microusb for power)
I put together my Xeon e3 1231 v3, GTX 1080 and was surprised how easy it was to put the whole thing together (also pretty fast); only problems were the riser bring a bit stiff and finicky, I put it in the wrong way and tried to remove the PCIE and took me more force than I would have liked but...
He needs that IPad monitor (its a mod) https://smallformfactor.net/forum/threads/my-modded-ipad-display.2680/
Basically Ipad +$30 adapter and little DIY (pretty easy with a teardown video)