I understand the hesitance to say something then the exception to the rule appears. I'm sure that all case manufacturers go through this to some degree. At a certain point, I think it ceases to be the case's fault and becomes the motherboard's problem. I also agree with only having a single set of PCIe extenders. I still don't really have a clear idea of how the routing holes look so I'm just speculating how it might look and if it would be any easier, even with the same length ribbon. The fact that you include such a high quality PCIe ribbon with your products is already a huge boon to us customers (that Salvo logo on them is pretty nice too).Yes* (mATX support) and Yes (shorter PCIe extenders).
Edit: I want to say that although the extenders won't have to be as long, I'm probably not going to keep varying lengths in stock just in case someone wants to install a mATX instead of a standard ATX board. I think it best I buy as many of the same length cables to help keep costs down and if they are longer than they need to be at least they would support an upgrade if the customer decides to switch to ATX from mATX in the future.
*I want to officially support mATX and the standoff pattern should do that but I know as soon as I say it's supported, there will be some random mainboard that might not fit. Unfortunately, I don't have the resources to buy all the motherboards to test-fit, but I will do my best to support all that I can.
On a different note, I was going to take off one work day this week to try and make all the desired changes to the S700 in Solidworks but alas we have visitors this week and I won't be able to take off. Also, without going into detail the government shutdown will impact the amount of capital I have to invest in another prototype. This is probably for the best as it will force me to take my time and really critique the design before I submit it again for another round of prototyping.
I'm still hoping to be able to take off a day next week to work on the design and make some solid progress. I've already updated it to be 0.5" taller and about 1/8" wider on each side. I've added the front panel pushbutton top and centered as well as added a new pass through hole for the PCIe extender(s). I've also backed off the standoffs from the rear IO cutout to provide more compatibility with some of the mainboards with IO covers built-in (Asus primarily). I'm not entirely sure I have the spacing correct, but I know it's going to be better than the S401.
Take your time for sure! Myself, I've finally accumulated leave to our "use or lose" limit so I can actually feel okay about taking some more personal days here and there. It'd be real nice if I could get onto our compressed work schedule... longer days in exchange for one off here and there. Then my Instagram modeling career will really take off! <cue derisive laugh track>