As the video shows, its ok speed to me. of course most people would want to go faster. I dont plan on making it anything past 20-25 mph.
modding a battery pack should be pretty easy, or i could use my lipo packs. Does water get into yours? Should I bother trying to put some water proofing to it?.

40 amps and no lower than a 15 turn motor, so basically i can try almost anything above 16 turns.. what Kv should I go with?

What if I go with a high turn motor for higher end top speed? ie 20 turn?..