I like the look of the board! Does almost exactly what I need.
I could probably use it as specd, but I want a bigger battery, and the option of a charging port not tied to the Pi power. Here's a pic of the component layout for power that I'm considering. Please excuse the poor VISIO diagram, I'm a programmer, not an EE. This should allow for full power charging while still providing full power to the MightyBoost (the DFRobot Power Module is capable of a sustained 5A out).
The downside here is that I don't get a power reading from the External battery pack to the MightyBoost. Not a huge problem as before I didn't have the UPS ability in hardware anyway. I was planning to handle that in software by tying the power status LEDs from the battery pack into the GPIO pins on the Pi. Not the most accurate solution, I'll admit.
What would be nice would be some way to disable the charging circuit on the MightyBoost, then I could tie the battery pack directly into the LiOn-In (bypassing the boost-converter on the pack) letting MightyBoost handle power level monitoring (I'm assuming you're doing a voltage based solution) while letting the circuit that came with the pack handle the charging. The Anker E5 pack that I'm looking at is 15000mAh, so charging at 200mA or 500mA would be, well, painful.
Alternatively, you could let me dump 4A into the MightyBoost so I can just hook a huge battery pack up to it directly.