A vxl motor would fit the bill quite nicely- may not be the best motor in the world but the kv ( 3500kv ) is perfect for normal 2s lipo use, super-fast on 3s, so 7 nimh cells should be just fine, so long as he doesn't act like a noob again and actually re-gears it according to traxxas's instructions:
Chances are it'll run a fair bit cooler too compared to a little 5000kv thing the same size..