unsolder battery leads from MMM?
 

Is there some trick to getting the original battery leads unsoldered from the MMM pcb? I am using a 100watt soldering gun and it's like the solder doesn't want to melt all the way through so I can remove the wire. The heatsink on the MMM seems to be sucking up all the heat from the soldering iron before the solder can liquify completely but it has to be possible right?

100 watt gun is all but useless for stuff like that.

100 watt iron, maybe.

I'm assuming you understand this (soldering on the board) voids any warranty on the ESC. Why do you want to do this? Longer wires? I've asked about this before and was told Castle will replace wires on a Mamba Max for $15 wiring charge. Probably do the same on a MMM.

Extending the wires is easy, if that's what you are planning on doing- just do a neat butt-joint with some more 10g wire & insulate with heatshrink tubing. Pumping lots of heat into the PCB without getting the wires off straight away is just gonna cause damage or desolder some of the smaller components..