The Killer is always the same , refrigeration.
The newest car style batts may become useful after thousands are rebuilt , but the fear of a computer caused fire is real.
I believe one answer could be a better eutetic plate design.
I was friends with Mike Adler of Adler Barbour and he had a custom unit made by Dole that only took 15 min to go all frozen.
His shop had limited electric so only a 2 hp compressor could be used .
The hassle with most eutetic plates is a copper tube is installed bent back & forth that does the cooling.
Sadly the tubing it ices up rapidly , and ice is an insulator, so even with plenty of power total freezing is not all that rapid.
It takes 2 hours on our 90/90 to be frozen for a 4 day hold.
Instead of tubing Mike had a copper plate with freon passages similar to an evaporator plate in a house fridge.
The plate was doubled over so internally the ice only could be 1/2 to 3/4 thick , so it froze rapidly.
Perhaps a mfg. will run with the concept and produce a well insulated reefer that would only need 15 min of house current per day .
ALIBABA , you listening?