On the external charger, I would not include that in the standard package. Offer a generic charger on the side If needed, but the internet is floaded with chargers for 18650 cells. Lots of people already have a battery charger. And for those not willing to get one, they can charge in the unit itself. I for one, will not use whatever external charger you include unless it's superior quality to my Nitecore I4.
On the max temp, could we convince you to get it up to 430°F again? Or does that compromize the current design?
This is a verry promissing device, hope to try it out soon!
Cheers