The MM esc will comfortably handle 5S A123, or it should anyway. The problem that you will run into is over revving the motor.

Castle creations set the battery limits on the Mamba Max systems based on the number of rpms the motors will turn at a pariticular voltage. The maximum rpms recommended by Castle is 65,000. With a 4S A123 setup, you will likely exceed that rpm limit. I also have to warn you that the motor will likely run hot too. It's also going to be more sensitive to gearing.

Unofficially, I was told by the guys at Castle that they test their motors up to 80,000 rpms. At that point, the motors start to tear themselves apart. If you can, you might want to try out a 4600 motor on that battery setup. It won't run as many rpms, but will be far more tolerant to gearing.