Nice to still see some interest in this case idea. For now it's still in a design and concept stage but the biggest step to prove this idea through is to buy a mini STX board. However with my APU upgrade also stalled for budget reasons it won't be easy trying to make purchases for two motherboards at the same time.
Because of that, I will dust off the old designs and get some price estimates for the case parts, especially the frame.
I have an accurate STX 3D model from Shappire.