[hemiblas]

The razor scooters already have a low voltage cutoff. At 6S it should be fine. I run 7S on something similar and it works fine too, but lvc will hit at a lower voltage than you would probalby like. It probably wont work over 7S because they have a high voltage protection, but your kid will always want to go faster. The 5k pots are only used on the brushless motors. I'm pretty sure thats a hall effect throttle. I havent figured out a way to get that to talk to a CC controler. TNCscooters has some good deals on different controllers if you wanted to swap it out, but there is good info there on how they work since they have all the spec sheets.
LVC on those type controllers are around 20.5 volts according to a bunch of spec sheets and they are usually plus or minus a volt. You cant run SLA's down either or they go bad too. I've been running lipos in my scooters for a while and they work great. Those controllers limit the voltage to keep accelleration under control and keep the motor from burning up. If you put a CC controller on that thing it will probably wheelie on demand.