Simple and inexpensive battery heating and cooling in a harsh environment?
What are your recommendations to keep batteries warm and cool in a
  harsh (hot/cold/moist/dusty) environment, to ensure long cell life,
  that are neither complex nor expensive?



Choose the device and technology that is appropriate for the environment by examination of the data sheet. Don't skimp on this! Talk to manufacturers and tell them what your expectations are.
Look for similar applications and do some research as to what other people have had success with. Sounds like you have started this process
Only choose devices that are made by manufacturers who have a reliable record for this technology
Purchase the components from a reputable supplier/distributor that offers a decent support facility
Apply the device by taking into account the recommendations in the data sheet and any other guidelines the suppliers/manufacturers provide.