Help for design of a battery management system

Attached is the sketch of the concept as I understand it.  I'd like to have multiple options to deliver the charging or powering voltage (USB, Micro-USB, etc..., so the incoming voltage would be be 5V).  Then this would feed into a battery management chip that would monitor the status of the battery and charge it if necessary.  As for the battery itself, it will provide an input to a regulator to step down to 3.3V for standard electronic components.  At certain times, an output from the electronics will open up a transistor that connects the battery to a motor that can run on 5V - 12V.  So the nominal battery voltage can be anywhere in that range, but I'm leaning towards something like this.  As an optional function, I'd like the system to also be able to charge an external device off of the battery through a USB connector.