Ebay MT 100 amp esc

[BrianG]

A fan doesn't draw nearly as much current as servo(s) do, especially in something heavy like a MT. So, even if you can't (or don't want to) move the fan off the internal BEC, just moving the servos to a UBEC will help.

As to other ESCs failing because of the BEC; I wouldn't assume that just yet. MGM has a UBEC in it and it works fine. I don't think anyone has truly nailed down the BEC as being the problem on the MMM. The one on your ESC is a linear regulator, which is much simpler yet a lot less efficient on anything over 2s, which is why it gets warm.