replacing a gas engine with an electric motor and installing a battery pack is not hard. The EV1 was a pretty bad car. The real secret sauce of modern electric cars is cheap Lithium Ion battery packs.
The EV1 predated the Roadster by a decade. Had GM been improving the EV1 for those 10 years, including Lithium Ion batteries, GM would have been far ahead of everyone . . . had they just kept going with a technology that was inevitable. Where would Cruse be today had they continued with this new technology that is inevitable?