The MAX17055 alert pin is an active low output. The drive range is from the supply (BATT+ ) to GND. This limits the high side FET to be a PFET.
A PFET solution will require an additional inverter on the ALRT pin output to pull the gate low to allow the charge/discharge of the battery when no alert condition is present.
This solution will make the system more prone to faults, hence the ALERT pin cannot be used to control the battery charging or used as master to control any slaves attached to it.