The MCP2200 is a good chip for one off or personal use but it has known driver issues on several windows platforms. So its fine where you have control of the operating system, but it really would add a whole bunch of support issues in in a board public distribution.
With all the connection issues already one of the single most prolific issue postings in regard to the Arduino on the board, I wouldn't want to add it to a larger mix in a board I was selling.