imagine there was an OSHW mini ITX board for MNT Reform compatible modules, similar to turing pi 2 (which is awesome but afaik not oshw? correct me if i'm wrong). would that be interesting for you? or would you prefer a different form factor? (modules would be networked, and module 1 could also be a BMC.)
@mntmn I'm a big fan of the mini-business desktop form factor (see https://www.servethehome.com/hp-elitedesk-800-g4-mini-tinyminimicro-guide-review/ ). I own a few of them and the design is fantastic. They have a design like a miniature rackmount server (heatsink on cpu and separate blower fan), and from my experience they are super easy to work on. Also, the size is probably more than large enough for a 2.5" sata drive (if desired). Also, they stack nicely.
@mntmn I don't think there is a spec per-se, I think it is more of a form factor (e.g., a mid-tower). That said, they are often referred to as 1L desktops as they occupy roughly that volume. This page might be a good inspiration for the dimensions of the board and enclosure though:
https://www.asrock.com/nettop/AMD/Jupiter%20X300/index.asp#Specification