I have a xx4we and it can't be massively different from the xx4. I have the magic setup and it runs beautifully.
You can run brushless but pretty mild, say 10.5t, without melting down.
I'm assuming that unless he hasn't done his homework and has got crazy by plugging in 5.5t with wrong gearing etc...the xx4 is unlikely to cope with that.
Can't really comment about the stripped threads but I don't think he has a good case especially after how long has passed! He may have modified it compared to when you last had it. You have also provided a good description so I can't see it getting far.
Bottom line..you should know your stuff before buying. That's why these forums are useful
There are lots of deluded ppl putting 11.1v 3s lipo and 4.5t brushless for "speed" in off roaders. Unless you like to see your car melt and run dizzy in circles this is pointless....