60 mph mamba brushless setup for e-maxx, would this work?

With the 8XL, you might just want to try starting off with 14 cells. That's about the equivalent of 4S lipo. You're going to be surprised with the performance.

On another note, I can understand your caution when it comes to using lithium polymer. It can be intimidating. You could look to the A123 cells, which are readily available in dewalt 36v battery packs. You get 10 cells in a pack and that would make for a nice 5S2P setup. With a lipodapter, you could use a plain old nimh charger to charge the pack. The A123s won't explode or catch fire like lipo will, but are capable of amazing current levels and with the right charging setup, will charge in about 15 minutes or so.