I presume that Statorade is primarily meant for hub motors equipped with external controllers, so I'm not sure whether the internal controller would be affected by the Statorade if some of it found its way into the controller housing in the centre of the stator.
I'm not sure about the MP5, but the MP Edge definitely has a "Z" shaped milled slot on the side cover flange to allow the air to move freely between the inside of the motor and the outside
(and vice versa).
If you put Statorade in this motor, you would have to seal up this breather slot to prevent the Statorade from leaking out, and if you completely sealed the side cover joints, the only place for the internal air to go when it expands as the motor gets hot, would be through the axle bearings.
As the motor gets hot, the expanding air would then have to force its way out though the dust seals on the bearings, and washing a warm motor with a hosepipe at the end of a dirty ride would cause the air inside the motor to quickly contract, causing air from outside to be drawn into the motor through the bearings
(accompanied by some of the water from the hosepipe).
This would not be very good for the longevity of the bearings.
Also, the standard Magic Pie does not tend to overheat with the default recommended 25A maximum current setting, so additional cooling measures are not really needed.
If you are going to use an external controller with higher Amps and Voltage, then it might be worth considering. But I can't imagine that GM would be prepared to modify all of their motors just so that the occasional customer can add Statorade.
If you are planning on modifying the motor to produce a lot more power, then it is your decision if you wish to modify the covers to allow Statorade to be injected.
My Magic Pie II has a modified internal controller that delivers up to 60 Amps
(and does not have an external cooling fan like the MPIII, MP4 and MP5 have) and I have never had it overheat.
Alan 
