Use MOSFET series resistor instead of shunt for current measurement
MOSFET's on resistance is not very accurate and not stable over temperature. So if you calibrate and compensate- go for it. Or maybe it's just good enough. LiPo itself probably like narrow temperature range, maybe in application you are limited to 25-35 degrees or something. 

Keep in mind, that in two years your purchasing people will ask to replace the MOSFET with something else- and you can't, because there is no same MOSFET in the world.