So could you not use the Roadster engine and have it mapped?
smart 4-2's and roadsters all use the same engine and gearboxs and come in 600cc and 700cc capacity. the brabus versions are 700cc and are about 100bhp. a non brabus 700cc like mine is 80bhp standard but costs £300 for a remap to 100bhp.
ferrina, why don't you use a jap 3pot/4pot - more power, fuel injection and reliability. lighter too as all alloy compared to boat anchor a series?