Hello,
FIRST
As You probably know Renault Zoe have 3-phase 43 kW onboard charger.
smart for two electric drive have about 3 kW onboard charger. Optional 3-phase 22 kW cost about $3500.
Tesla Model S have 10 kW onboard charger. Optional upgrade to 20 kW cost about $1500
So in smart, upgrade...