Mini ITX Computer Case - Modular / Stackable

This is a project I have been working on for some time. It is the original purpose for which I bought a 3D printer and is finally coming to fruition. This design will require onboard power or pico-PSU style power supplies, for now.

Project Goals:
Modularity - Inspired by Legos
Stackable - Each self-contained module can be stacked in a tower
Minimalistic - Small footprint, as little wasted inner space as possible
Print-ability - No supports, little waste, low warp risk
Marketability - Anyone interested?

There are two version to choose from:
The slim version is for Slim-ITX boards and does not allow space for hard drives.
The standard version should fit any ITX board and has space for two hard drives with the included bracket.

Future Plans:
I'd like to add modules to hold various PSU and VGA cards. This will enable this case to be used for a gaming or desktop style system. If anyone would like customization, please message me.

Additions:
3.5 inch Hard Drive Module