There won't be a big diff in weight between the EMAXX and a 1/8th buggy so the HVMAXX should work just fine. It seems thermal issues have always plagued the HVMAXX no matter what application. I believe if you disabled the BEC and used a UBEC you may be able to reduce some heat.
I believe Novak has an external capicitor available that should also reduce the HVMAXX's thermal tendencies.
This may sound like a dumb question but: Is the electric motor/diff mounts for sale in the shop here reversible? Meaning can they be flipped either direction so the motor can be placed on either side of the vehicle.
I'm talking specifically about the one for the Mugen mbx5. I'm sure it's not, but I can't tell which way it should be turned by looking at the picture.