mars is too small, not sure about how large that sepex is, but most I've seen might be too small for a bike that heavy. I think the AC15 at 96V would be an OK option for such a heavy motorcycle.... but I'd actually be considering a larger motor, like a larger ADC, D&D or Netgain motor. The AC/sepex motors are good for motorcycles around 400lbs or less, but they'd be stressed and could overheat if there's a higher load, especially pusing a 600lb vehicle at highway speeds with rider(s).... with more frontal area than a moto.
For BMS and Lifepo4, we've got tons of different battery options, as well as BMS to match.
www.evcomponents.com.