Idea: heat and cool the seats and dashboard directly. I estimate 50 watts thermal per passenger,(max). Average passenger cooling watts probably closer to 35 watts thermal, even on 120F Phoenix days.
Cool the dashboard to a thermostatically regulated temp of 95F.
I would suggest a water chiller such as used for chilling down fish tanks, but obviously adapted for DC input power and compactly packaged.
Cloth steering wheel so I don't have to grab a scorching hot piece of leather in the Phoenix hell heat.
On heating side: 50 watt resistive heaters per seat. Resistive heating element in the steering wheel. Resistive heating element (or electronics waste heat pumped?) for the dashboard & window defogger vents.