PYBv4 opinions and suggestions by JohnHind

1. The board is too small to be an effective baseboard for shields/skins like Arduino (particularly if skins are half size as suggested). Better to make it a DIP module like Mbed designed to be plugged into a baseboard.
2. This implies that the connections should be pins on the underside of the board only. However the servo PWM pins could be double ended so they have dual use for servo connectors on top of the board (with the servo power pins on the top-side only).
3. I like the symmetrical IO concept with left and right sides rotated by 180 degrees. But rather than skins on top of the board, use a split baseboard. You lay two baseboards side by side with one rotated 180 degrees with respect to the other and the PyBoard plugs in on top as a connecting bridge. The baseboards can protrude out from under the PyBoard by as much as is required for their specific circuitry.
4. With careful design, the PyBoard could also be able to be mounted on two standard mini-breadboards e.g. Cool Components Breadboard laid side by side in the same manner as split baseboards. It is already just the right width, it is just a matter of avoiding any obstructions on the underside of the board. It would be possible to displace the 3v3 and GND pins so they engage with the breadboard power busses, releasing two extra pins from the 16 for IO. This would also provide better structural support for a split baseboard assembly.
5. Rather than (or as well as) a vbat pin, provide pads/vias for the user to optionally fit a CR2032 battery holder. At first sight, this seems far too big for the board, but a holder such as Adafruit CR2032 Battery Holder could be glued on top of the microcontroller chip and soldered with short wire tails to the board on either side of the chip.
6. The accellerometer should be optional - i.e. make the IO it uses available on pins as well. It can be removed if not wanted, or a version of the board can be produced with it omitted.