I expect to be getting the next revision of the MHVBoard in the coming months, and am currently soliciting user feedback/wishlists for the upcoming version.
The MHVBoard is based on the Metaboard, and does away with an external USB->Serial chip. Instead, it uses V-USB to implement USB directly on the main MCU for flashing. The supporting hardware is then available to user programs using V-USB, allowing them to implement low-speed USB devices such as keyboard, mice, etc (with some restrictions).
Schematics & board layout can be grabbed from our git repository, and a full description of the board & other useful info is available on the project page:http://www.makehackvoid.com/group-projects/mhvboard-arduino-clone
Any ideas that align with the project goals and are cheap to implement will be added to the wishlist for the next revision.